"Choking" to me is failure when the pressure suddenly amps up. Kansas St choked yesterday, for sure, because they found out that being #1 is so tough they could only handle it for 6 days. I think Oregon choked a bit as well, all they needed to do was win, although they played a tough team (I watched the second half, and if it wasn't for Cardinal fumbles it would have been a blowout).
Alabama lost one too, but had been ranked #1 for most of the season. I also think that A&M right now could beat any of the these other teams, but I don't think they would beat Alabama again.