Desco -- agree 100% that if you can get first round money, you take it. But I do think that guys can develop in college and improve their draft status, so there is something to be gained from staying in school. I know the D-league is becoming more of a viable option, but remember that 19 an 20 year olds leaving early are also competing with a lot of grown men for those roster spots, who have been training at their craft professionally for years. Plenty of kids get phased out who make the leap too early.
Omar Cook has made a lot of money overseas, as Foad points out. But had he stayed in school, improved his jumper and developed his game more, was there a chance he could have been drafted in the lottery, made even more money, and stuck around in the NBA longer (which is where all these guys eventually want to get)?