To get those quality recruits, most teams over-sign commits each year. Yes, almost all schools over-sign to varying degrees.
All schools and all conferences do it, but the SEC is probably does it the most.
Here's a great link regarding teams that continuously over-sign recruits: Over-signers
Auburn signed 112 players in four years ('06-'09). Quite a few more than the 85 allowed. But they do it every year. So do you think Auburn cut back the following year by only taking five (or fewer), commits to get closer to the 85 limit last year?
HECK NO! They signed 32 more in 2010. In your face NCAA says Auburn. I know they are accounting for those recruits who may not make it to the roster in a year, but this is still an unfair and illegitimate practice. Is the NCAA rule against it so hard to enforce?
Top 10 offenders over the last ten years:
Auburn, Mississippi State, Iowa State, South Carolina, Arkansas, Kansas State, Ole Miss, Alabama, West Virginia, and Oregon State. The SEC is by far the most-rogue conference.
These schools take too many commits, then just usually cut the least talented of the bunch. Some players won't academically qualify - but that doesn't justify over-signing. This practice is against NCAA rules.
So if the NCAA has looked the other way for as long as anyone can remember, then USC should join in the fun.
How are things looking this year? So far, Cincinnati and Miami (Florida) have signed 30. Alabama already has 27. So does UCLA (the Bruins only have 17 available spots, but they are over-signing anyway).