A great salary dump can still be a great trade. In this case, it was 1000% necessary to clear the swamp (the thought that we could still be paying Carl Crawford gives me the heebie-jeebies), and doing so paved the way for the 2013 title by allowing us to add the likes of Napoli, Victorino, and the rest.
I wouldn't say we got nothing in return, either. It's easy to forget now, but De La Rosa and Webster were promising arms at one point, the former of which has stuck in the majors as a back-of-the-rotation type starter. Those two helped us get Miley, who had a decent season and then got us Carson Smith. I think the other two guys went to Pittsburgh in the Hanrahan/Holt deal.