Here is what I see in defense of the team getting Cantu.
Currently he has 5 OF that are worthy of being in his starting lineup (Soriano, Upton, Dukes, Lee, Vlad when he comes back in a week or so) and a crap 1B (LaRoche). By doing this deal, he gets Vlad off the bench and puts LaRoche on the bench.
Since beginning of '08:
Cantu: 204 hits for ..279 average, 109 R, 127 RBI, 37 HR, 6SB. On a decent up and coming team, probably dual-position eligible, 27 years old.
Lee: 176 hits for .318 average, 75 R, 126 RBI, 34 HR, 4SB. On a declining team with a bad offense. Only eligible as an OF which is deep. 33 years old.
Granted, Lee did miss a month last year with injury, but those lost stats can be considered the discount in value that he should receive for being an older player that is more of an injury concern.
One point that was made was the question of whether Lee could bring in a better 1Bman. Well, maybe. But sometimes a trade in hand is worth two trades in the bush. A deal got done, and rather than dick around trying to make this upgrade happen for another two weeks, the owner got the deal done now and upgraded immediately. Besides, your job isn't to decide whether or not these teams both made the best deal that they could. Your job is to make sure that trades do not compromise the integrity of your league. To me, it is fairly clear that this trade has not done that.