The lack of a powerhouse conference gives USC an edge. As Yertle (I believe) pointed out, if you give a team 80% chance to win each game, its chances of winning all 11 games is 8.6%. (See his post, somewhere, for how relevant the 80% thing is, and how you get from 80% to 8.6% - though I think he said 9% - I just carried out a decimal place.) USC, being in a weak conference, may be able to change 5 of those games to 90% chance of winning. That nearly doubles the chances of winning all of the games (15.5%).
I don't know how Vegas comes up with 8-1 odds or 100-3 odds or 4.5-2.9 or whatever. But I'm sure that USC's Pac10 schedule plays a big part in picking USC the favorites to win the BCS, again.
Good call, Mili. I guess I should have added to my post that they ARE actually a good team, which plays a very large part in Vegas' picking odds.