Yes, there have been pornographic movies in 3-D before. But I believe only in green-red 3D, not modern 3-D.
Caligula was... A bad movie. I say this having seen somewhere between half and two thirds of it at a college film festival screening. All moral issues aside, it's just badly shot, badly acted, the color makes things look even more lurid than the content, and the content is virtually devoid of artistic or erotic value even, I suspect, if you have some fairly odd fetishes.
I don't necessarily think 3D pornography is the end of Western Civilization, but for the love'a Mike, can't they aim a little higher?