If you wonder why teams shouldn't give up on players with at least SOME potential (cough, Derrick Williams, cough), then look at this board -- 19th best guy on the board: Andrei Kirilenko. 31st best guy on the board - Corey Brewer. 33rd? Al Farouq-Aminu.
Derrick Williams has a 14.5 PER and 3 Win Shares. He slightly improved last year. Will he EVER be worthy of the #2 pick in the draft? Probably not, but should you just toss him away for nothing? I would say no - because your other option is to go out and fight on the free agent market for guys who are pretty much the same guy as DWill.
Look at Jarrett Jack, Monta Ellis, JJ Redick - their advnace stats are not substantially better than DWill's and Ellis (for example) just opted OUT of a $11M guarantee for this year!!