Microsoft has a slightly different content policy on their machine.
They keep a very tight hold on what may live on their platform, and generally they try to "monetize" whatever goes on it.
No web browser, no youtube, no BBC iPlayer.
They have started to slowly embrace the concept user-created-content (and eventually free-as-in-beer content) through XNA, but the real ethos of Xbox is the ultimate walled-garden, money-tree entertainment device. Time will tell as to whether this is the best avenue for them to go down.
Theory is gray, but the golden tree of life is green. -- Goethe