A lot of NBA and college teams are building their bridges to the 21st century on youth. But, as more raw undergraduates leave college early for the pros, those bridges are crumbling at the foundation. The driving force behind all this has been NBA money. Teams inhabiting the NBA cellar have nothing to lose by throwing their money at one of the undergraduate sensations making college broadcaster Dick Vitale do flips.
Like it or not, prior to the 1990's, the NCAA did provide a proving grounds -- or, god strike me dead, a "minor league" -- for NBA prospects. It was not just a bastion of idealized amateurism, as the NCAA hoped, but a way for young kids to prove their talent and character to their potential future employers in the most exposed professional league in the world. Now, as much as the NCAA hated being a proving ground, it is now dreading watching that proving ground move to the NBA itself.
College players are leaving for the pros in droves now. The reason for this is complex, but it is most related to the rookie salary cap instituted by the NBA in 1995, which limited pro teams to paying about $3 million dollars per year on a rookie. With this rule, NBA teams realized that unproven talented undergraduates were no longer as big a financial risk, at least compared to the $8+ million they were beginning to pay them in the years prior to the cap. College basketball players -- or at least their "advisors" -- realized this, too. Talented but raw college players knew that they were more likely to be drafted since they weren't as risky. All of a sudden, marginal prospects felt that the worst outcome of leaving school would be that they make the rookie minimum; contrast this to the prior worst outcome being not drafted and left unemployed holding a sign saying "Will play ball for food".
What this is doing to the NCAA is robbing it of all the players that have the potential to be professionals (except those that go to Duke). What the NCAA wanted -- a truly amateur game -- it may soon get.
What this is doing to the NBA is diluting the talent pool and making it much more difficult to scout prospects from college. Because the college talent pool is diluted, average prospects look good and good prospects look great. Recent NBA teams drafting in the top 10 have not improved as much as a result of their high draft picks because the best players coming out of school aren't as ready to face NBA competition. It's a small effect, but it is noticeable.
Finally, what this is doing to kids is putting them on a rather risky career path. A college athlete benefits from being in college even if he does not graduate, just by becoming a household name to potential employers. An athlete that leaves school early loses some of those benefits. An athlete that leaves without the blessing of his coach is taking a very big risk. That athlete has been told that he could be the key to taking an NBA team to the 21st century, but most of them are just having a bridge sold to them.