maybe it's because they chose not to use gamespy servers?
I don't know, IGN and gamespy and all this stuff appear too closely related to me to be able to distinguish a difference.
I was able to patch DAo w/o impulse

But then what games require Impulse for patches that aren't sold through Impulse / aren't made by Stardock?
What you're comparing MW2 to are the equivalent of games bought through Steam or Valve's own games. Which are clearly a separate matter. If third party games started requiring Impulse and these titles were sold through Steam / other DD site then it would be hypocritical.

Well, they're all one and the same company, that's why.

That's what I'm asking. I only have one non-Impulse bought Goo protected game, and there are no patches for it; so I don't know how it works. But if such bought games do require the impulse client to patch then Impulse are no better than Steam.

In the US simply having a monopoly is not illegal, only abusing that monopoly is. There are quite a few monopolies that all of us deal with on a fairly regular basis: electric, gas, and water (basically all utilities) are typically monopolies; cable companies also tend to have local monopolies all across the US; phone companies also tend to be monopolies (at least as far as control of the actual infrastructure goes). Again, it isn't illegal, but it means that the government (theoretically) keeps a closer eye on such companies, and (again, theoretically) regulates as necessary if they start abusing their monopolies (such as what happened a couple decades ago with AT&T, and what is currently happening with Intel).
As for anti-competitive practices, generally bundling is not considered anti-competitive unless a company has a monopoly or at least has market dominance. The reason for this can be seen in the very case we're discussing in this thread. Without a monopoly or market dominance, when a company tries to pull this kind of shit their competitors strike back, making it disadvantageous for businesses to sign on to the bundling. This is competition at work, ergo the argument that anti-competitive practices are taking place falls flat. Basically as long as there's adequate competition the situation sorts itself out, as we're currently seeing. It's only when there's no longer adequate competition to keep such actions in check that the government has cause and need to intervene and levy charges against a company for abuse of monopoly and anti-competitive practices.

I find it absolutely hilarious that GameSpy, OF ALL PEOPLE, accuse Steam of being a Trojan Horse.

THANK you Navagon, you just got to the root of the issue. If a title is "third party" but requires the installation of a particular front end which comes with a store which would RIVAL the store selling the game, it makes perfect sense for those stores to back off.

The problem is, MW2 is still going to be a huge PC game...I don't really believe that the casual fan gives two shits, they'll still buy it in droves. And by not selling it at all, the other download services are potentially shunting business to Steam because if you want to buy it online you have no other option now.

You don't seem to understand what a monopoly really is. None of the examples you provided are monopolies in the least. All utility services do have competing businesses and are not really monopolies; the electric company competes with energy co-ops and things like home solar and wind; the gas company competes with home heating oil and propane services (and the electric company, technically); cable companies compete with satellite and other entertainment services like FIOS; the phone company competes with VOIP and cellular services. A monopoly is a company that is the sole provider of a particular good or service or has sufficient market control of a good or service to dictate its distribution, use and cost outside of free market demands. None of those businesses fit that description at all.
You also seemed to have missed the reasoning behind the refusal to sell the game. Those other services do believe that bundling Steam is anti-competitive, but as I said, proving that would be difficult. Steam really doesn't have the kind of market share (that we know of) in order to show that the bundling has impacted it to the point that it could lead to a digital distribution monopoly.Because of that, rather than try to take it to court, they are countering Valve's potentially anti-competitive practice with an anti-competitive practice of their own. Neither one of them has actually done anything that is clearly illegal, but the grounds for an investigation and close monitoring of the situation may be there. We'll probably never see anything as exciting as the Microsoft case come out of this, but we may see Valve forced to take steps to remove even the semblance of anti-competitiveness, before it gets to the point where lawyers and judges are involved.

By that reasoning Microsoft wouldn't be a monopoly either, since it has competition in the form of OSX and Linux. Yet as far as the law is concerned it most certainly is a monopoly, and has been convicted of using its monopoly to stifle competition both the US and the EU. Feel free to do some reading from whatever you consider an authoritative source on the matter, but the short version is that it doesn't require 100% market share to be a monopoly, but only having a large enough market share (usually anything north of 60-70% is sufficient) so that with regards to a specific class of product or service the company can significantly influence the overall marketplace through its policies.
If other companies in the marketplace can mount a meaningful response to another company's actions then that is competition in action. "Something bad for our business" is not anti-competitive, even if it makes a nice soundbyte. The nuance to the situation that's easy to miss is that the same action can be both anti-competitive and not anti-competitive, depending on the state of the market it occurs in. For example, if Steam had a monopoly or market dominance then this bundling would be anti-competitive as not only does it move more people to Steam, but any action taken by other companies would be ineffective and simply harm those companies due to Steam's market dominance. But without market dominance the response by other companies can end up being quite effective, as the publisher is left with the choice of bundling with Steam or losing out on having their product carried by distributors that make up >60% of the digital distribution market. It's only if this competitive market response is shown to be ineffective that a case can be made that this bundling is anti-competitive (as the failure of the response would show that Steam has enough control over the digital distribution market that it can control actions within the market significantly with its policies and with other companies in the market having little recourse).

I'm reminded of the PC version of GTA IV at this point. How many third party services was it that it required?

Two; Games for Windows and Rockstar Social. If anything, that is an argument FOR Steam (or some other incredibly popular digital distribution platform with support for matchmaking, achievements, and all that jazz. So Steam :p). It already does what most developers need their services to do. The only thing Steam is lacking is support for fancy profiley thingies where everybody can see that you just boinked the crap out of the French Bard.
I also kind of wonder why Impulse being a sneakier version of Steam would remind you of the debacle that was GTA4's service requirements :p

Except of course that if you bought it through Steam, it needs those two AND Steam, correct? So not really a good argument FOR Steam, I feel ;-)
In fact, there ARE no good arguments for a MANDATORY third party service, from a consumers point of view.
Oh, it was just the whole mandatory third party service thing.

That's not including three usages of SecuROM - disc check, online activation and release date checker.
Yes, Steam would have been a better bet had they actually ditched the rest and just used Steam. But Rockstar seem too insanely paranoid to rely on the one 'service' alone.

Rockstar/Take2 are ridiculous. Thank God I found the GTA 4 launcher that Securom leaked by mistake (removing disk check), otherwise I might have sold the game.
The Bioshock DRM is still annoying as hell. Posted about it in their forum but their staff haven't been active for a week. If you're a forum member, please chime in with a word of support!
http://forums.2kgames.com/forums/showthread.php?t=48225

Is that GTA launcher still doing the rounds?
I've got Bioshock. But it's the 'clean' Steam version which I got for £3 during their sale last year. When I got the retail version my AV reported the Bioshock exe as a virus. That's why I kept my AV ever since and immediately returned Bioshock. :P