Last opening line they were underdogs was the '03 opener at Auburn (+3).
The key to this game is injuries and match-ups. These teams seem to be going in opposite directions in terms of injuries. Oregon has some key skill players injured. SC has been getting alot of players back last week and this week - 6 just returned to practice today supposedly. I'd check out the status of both teams injuries during the week.
As for match-ups, it seems like SC just matches up well with this Oregon team over the past few years. Team speed on D and a really good run defense is the key to stopping Oregon's spread attack and it happens to be SC's strengths. Last year, SC held Oregon to 2.2 yds per rush and they return the basically the same front 7. SC still has banged up corners, but 3 of their top 4 LB's were injured up until last week. They all played some vs ND. If they are healthy, I would expect the Oregon run game to have a tough haul. They also faced a similar O in Seattle a few weeks ago with a banged up D and held them under 200 total yards so they have some recent experience, although against a much weaker opponent.
As for USC, the OL is really decimated (although they might get back 2-3 OL pre-season starters this week) as are the RB's, there is now a controversy at QB and the recievers are still raw. One QB has very little experience, the other one has a bad thumb and a habit of getting rattled under presure and making bad decisions at key moments. Not exactly the best choices for a team going into a hostile envirnoment. As bad as Oregon's D is, there is the potential for a bad day for the USC O. It will all come down to the O Line's health, IMO. So, I think this game might be lower scoring than one would think but I do like SC getting 3.