Well Steam is a way that it could work, as I don't think Sony and M$ would ever co-operate directly. As no Xbox games have Steam, I don't know if it would work, but PC and PS3 gamers can play Portal 2 together

"Isn't there a large Japan-angled trade show happening next week too? In a territory in which Microsoft could do with a big announcement to boost sales? Hmmm...
"

Yup cuz Japan goes crazy over Steam support!

I don't get it. What would someone do with steam on 360?

cross platform play of games like Portal etc, steam client match making, direct patches upgrades through steam .

Microsoft's hold on XBL is too tight for that to happen.
And it's not like it's all that needed, either. XBL is great.

Ok, some might like cross platform play. But xbl has match making and patches?

like you said what would some one do with steam on 360 and yes cross platform is the biggie but steam client matchmaking gives you another  tool that is directly linked to  valve made games  because at the moment that is really what it is about is Valve using steam to connect it's games whether they are on PS3,Steam or 360 so their audience has a unified gaming experience, that includes cross platform ,being able to put up free DLC ,and direct patching so when the patch is ready it can be done directly from the steam client for all at once rather than submitting it and each platform getting it at separate times.

i honestly don't want steam on Xbox at all. Steam is going to go monopoly just you watch!!!!

But they will grow and then bam!!!! Lets think like a company instead of the consumer.

I know that is true because Counter Strike Global Offensive is coming out for the Xbox 360 later on this year...
so its a no brainer, but Valve will use this opportunity to release their old games for DLC's