This story from the OC Register broaches the issue.

I think it is a no-brainer that he should go pro.

Mainly because:

1. It’s a very weak year for quarterbacks in the coming draft.  Outside of Matt Stafford, who is there?

2.  Sanchez is a pro-style guy and that’s what the NFL likes.  There are very few pro-style prospects out there.

3. He’s had his share of injuries (though nothing major) and staying healthy isn’t a given.

4. It appears he will have an outstanding year statistically, aided in part by a down year for the Pac-10.  Given the difficult schedule USC must play next season (with road games at Ohio State, Cal, Oregon and Notre Dame), it might be hard to duplicate such success.

Of course, if Sanchez returns, he will be, along with Sam Bradford, among the top Heisman contenders.