If you were wondering why only the Xbox 360 version of Street Fighter X Tekken is missing the four-player cooperative mode (2 local players online vs 2 local players), Capcom's Tomoyaki Ayano has an answer for you.
The PS3 version has this mode; Ayano says that they found the architecture of the PS3 to be "more conducive to implementing it." I'd bet that pisses some people off.
Ayano teases that they'll have more information on new updates for SFxT soon, so stay tuned. Maybe a fix?