i dont think teams try to tank the season. they probably give up after the allstar break but any coach will not allow his reputation to be tarnished in order to get a high draft pick. reason being, if there is enough complains he might be fired or the fans might protest resulting is loss revenue for the owner. i doubt any coach or owner would risk that.
even when d-rob and sean elliot were injured in '96, the spurs signed D-wilkens to carry some scoring load. the spurs were the third worst team but just got lucky in the draft. thats another reason why teams try not to tank because its not guarenteed that you will recieve the first pick. last year toronto was not trying to tank, nor were they the worst team but got lucky in the draft.
another thing, players have big egos, and they hate to lose. if management came to the players and asked them to tank, you know a few of the stars would ask for a trade, especially if they are in their twilight and looking for a ring.