Musichound, given some of the new sampling libraries put out by Kontakt, Garritan, and other companies using incredibly high quality recording gear, you can get some very realistic sounds. Consider that in the '80s, after Def Leppard's drummer lost his arm, his entire set, aside from a few cymbals and a percentage of snare drum work was all set up with triggers. And that was in the '80s. I dare you to listen to those albums and pick out what was and wasn't electronic.
I think, and any drummers out there can feel free to correct me on this, that most of the difference lies in the FEEL of the drums anymore rather than the sound. I can tell from time to time, but not often. If the drummer knows what he's doing and has a good setup with a decent compressor/limiter and gating device in his rack, he can effectively create the envelope of an acoustic drumset, which is generally what makes the two so readily distinguishable. It's most obvious on cymbals. As YYZ pointed out on another thread, you just can't have it fade into oblivion.