Stewart Mandel of Sports Illustrated looks at recruiting rankings, and generally found that the rankings don't really mean a lot. Sometimes they are right; sometimes not.
Back in 2004, I looked at Tom Lemming's rankings and found that they really were rather irrelevant in predicting future success. Everybody likes to point to teams that had highly ranked recruiting classes and then had big success with those players, but they never go back and look at all those rankings and evaluate all those rankings.
From 1993 through 1999, only 61% of Lemming's "Top 10" had top 25 football teams 3 or 4 years later, when those "top ten" classes should have been juniors and seniors. Oh sure, teams such as Florida State and Tennessee were both highly ranked by Lemming and had pretty good teams down the line. But there were some major misses as well. Notre Dame had top ten classes 7 out of 8 years from 1993 through 2000, but certainly didn't have much success with those classes. Alabama had top 10 classes from 1998 to 2000, but is just now getting back to prominance. And everybody's poster child for recruiting, USC, ripped off 4 straight "top 10" classes from 1994 through 1997, and couldn't crack the top 25.
Just remember that next week when signing day happens.