USC is 22-11-1 all-time versus the SEC. Of course, very few of those games have taken place in the last 10 years during the SEC's, cough-cough, rise to dominance. It's a well-known college football fact -- I would never make this up -- that SEC athletic directors run and hide behind their desks when the Trojans call, intending to politely ask if said SEC team would be willing to play a game.
Oh, a couple of teams didn't get the memo about ducking USC. Auburn and Arkansas both scheduled home-and-home series with the Trojans this millennium. The end result was four defeats by a combined score of 167-48.
Since USC went to Arkansas and feasted on BBQ pig by a count of 50-14 in 2006 -- the Razorbacks had spent most of the summer blathering about redeeming themselves after suffering a 70-17 beatdown the previous season -- no SEC team has been willing to schedule USC. (That Arkansas team, by the way, won the SEC West and finished 7-1 in conference play while the Trojans lost two Pac-10 games).
It's not hard to imagine what happened after that evisceration in an SEC stadium. SEC commissioner Mike Slive surely called a super-secret meeting to put an end to these shenanigans. Normally well-mannered and patrician, Slive surely slammed his fist on the table, telling SEC administrators, "No more scheduling USC! Why would we create a BCS system that favors us and still play USC, which is going to slap our butts every time, dagnabit!?"