Well if you ask Bill Simmons he says there's a distinction between tanking and what he calls "sand bagging." (and claims the Celtics did the latter) He says tanking is actively losing games, and sand bagging is putting yourself in a position before the season to lose games (or I guess it could also be adding dead-weight to ensure you sink to the bottom).
If you ask me, I don't think owners should be forced to lose money for a non-contender, however they should be doing everything in their power to win every game in the mean time, and put a contender back out there as soon as possible (even though those contradict each other). This is for the integrity of sports competition. I also think it's wrong to sit veterans who can help win you games for the sake of making your younger players better.
Simmons is wrong, a GM shouldn't be looked down upon for trading his aging players for draft picks and getting under the luxury tax. On the other hand, a GM is definitely sand bagging/tanking if they have the second lowest salary in the league and yet are trading Gortat when he has no backup to replace him.