Our league is a dynasty league where each team carries its entire 29-man roster over to the next season. So the only players that will be available in next year's draft are the ones that are not good enough to be on any roster at the end of this season or else are not in this year's Yahoo player pool at all -- such as 2009 MLB draftees (most of whom will not be in the Yahoo player pool next year either, at least not at the beginning.)
There will probably not be any highly desirable players available in our short draft, so there really isn't too much incentive to tank in our league when you really think about it. But you never know.
We have not had a problem with tanking, but it is wise to have a procedure in place before it happens to ensure there is no arguing if/when it does happen.