Isn't Google a big Ubuntu supporter? Considering the amount of custom code they've probably put into that OS for their servers, I doubt they'll ever move anything significant to OS X Server. When we hear about gMail's massive storage farms running on Xserve RAIDs, however, then I'll start to believe the two companies are best buddies.
Right now I think they're just acting on market pressure. Microsoft is trying to pick itself up and prep the launch of Vista. They're trying to push into Google's market with Live search and all manner of Web2 (used very, very loosely) stuff. The Zune isn't a big threat yet, but then the Xbox wasn't much compared to the PS2 at first. If Apple can get YouTube video into the iPod with as much ease as Podcasts are, then that would be amazing.
But YouTube on a TV (with iTV)? Are any of the videos even available in HD (or even Standard Def)?