Two is definitely not too many. For EDC, I only carry one, but I have carried two on a few occasions. When getting accustomed to a new carry piece, I do normally carry a secondary that I trust as a backup. I've never carried more pistols than I have hands - I'm not saying that its a bad thing to do so, but I had to set a personal limit. I'm all for options, and backup, but if I ever do need it, I don't want to spend too long deciding which one of my many carry pieces I'm willing to relinquish to the cops when they show up after the altercation. Precious seconds and all that jazz.
Now that I've been shooting for almost a year, and have experienced some malfunctions in a few autoloaders, I will say that carrying a small unobtrusive revolver to back up a semi sounds like a really good idea. Of course, that could just be my mind trying to justify spending money on a pocket revolver. And a range revolver. And a bedside revolver. And a .22 revolver for plinking.