See, I tend to agree with Phic on this one. I think it should change the way all teams evaluate the draft, and frankly, it would. For example, Oakland wouldn't have had the carry over of Jamarcus Russell tainting their organization 4 years removed from their selection of him in 2007.
I believe that there should be a rookie salary cap, but necessarily for the same reasons. It could be argued that, like stated above, it allows teams to "gamble" on some of those unsure prospects without a huge blow to their financial well-being for the next half a decade. However, would that really be helping the game? What makes New England great? I believe it's the draft. They drafted Tom Brady when no one else even wanted to try the lanky kid out. Also, year in and year out, we constantly see New England stacking draft picks like a motherfrakker, and every year they're in the hunt at the end of the season. If teams could comfortably pick studs coming out of college then most teams would only be affected by crap picks for one season, and then they get a do over; not to mention the fact that they would have yet another high draft pick in the following year. The reason the Bucs had an "unexpected" year last year, is because they had an excellent couple of years drafting, and they hit the jackpot on some of their bets. I'd hate to lose the competitive nature of the NFL draft because of a rookie salary cap.
With that said, I still believe that there should be a NFL salary cap. My reasoning may be simple but it is sound. I HATE seeing young kids getting paid the kind of change that they do these days off of only potential. It drives me crazy to see veteran players trying to compete with rookies, that may or may not work out, on how much they're getting paid.