Wow. Big news. This is a great move for both companies, IMHO. And good timing. The concern of course would be that Pixar has really had a great run as independent studio delivering blockbusters, and that being part of the Mouse House will, well, blunt their energy and fire.
I don't think it'll happen- I think they get off on making great movies, not anything else. However, I predict that "Cars" (Pixar's latest upcoming) will NOT do as well as some of its previous flicks (though it'll do ok by anyone else's standards). That'll prompt folks to doubt the value, but over time, Pixar will deliver, and it'll keep Disney relevant and healthy in the family picture biz (with the all the ancillary benefits and opportunities that implies).
More interesting is Steve Jobs as a media mogul. Its been building for a while - this makes it official.