Well, everyone else is throwing in his opinion, so I'll guess I'll toss mine in, too. First off, I wouldn't drop the slide on an empty 1911 because a) I don't need to and b) the allegedly traumatic operation would not have the alleviating effect of the feeding and chambering of a cartridge. I am careful about such things because I like mechanical things and I don't want to hurt their feelings. You might regard me as sort of a blued-steel version of a tree-hugger. I also like cats, dogs, and some other small animals, especially rug-rats.
HOWEVER, I try to temper my own "anal retentiveness" with some common sense. As far as dropping the slide to chamber a round, hell, yes! That slide isn't coming from any farther back than it does during normal operation. As for pulling the trigger while dropping the slide, while I recognize its theoretical correctness (I did it for many years as James Clark recommended for the Long-Slide he made for me), I know that PALADIN85020 correctly predicted some possibilities. I don't do it any more. The fact is that since IPSC, there has been a much higher standard for trigger jobs than in, say, the 50's and 60's. Hammers that follow just aren't acceptable any more, and really never should have been.
I don't recommend dropping the slide on an empty chamber, but I wouldn't lose any sleep over it. I wouldn't carry a gun I couldn't trust the hammer on.