DT's keywording service for old images was a dud to begin with. I'm sure the few images they managed to sell after re-keywording them were keyworded improperly in the first place, missing very important keywords (maybe even slip-ups of the contributor).
That doesn't justify the time consuming action of re-keywording them.
DT has implemented a bunch of questionable features on their site such as the "Stock Rank" game.
In the meantime DT has sunk dramatically and I wish someone with more business sense would have steered that ship 4 years ago when sales were kicking butt but now it appears to be just damage control although I don't see much success at this point anymore.