Maybe people realizes that the XBOX does more for media integration, have better games (and even have better graphics), and actually have friends you know who plays on XBOX Live.
I have a PS3, and besides Borderlands with multiplayer single-player missions co-op, there's not much else in terms for gaming. Blu-ray is pretty much the only reason one would need a PS3. And with BR players cheaper, the reason to get a PS3 is even lower.
Not to mention, I am a mobile game developer. Windows Phone 7 will be cross-platformed on XBOX and Windows PC. So I will probably need to get my own XBOX.
And this is without mentioning Project Natal > Playstation Dildo, I mean, PS Move.