Yes, as schwarze alluded to, there will be a blacklist on selected players. The blacklist includes all previously selected players from ANY edition of 12x12. Since the previous drafts are all in the forums, owners who do more research may have an advantage if these players are not blacklisted. A positive side effect of this is that we'll now get some new blood (player-wise) in this draft.
Please note that while the blacklisted players can NOT be selected in Round 1, you CAN use them as teammates if you like.