The sex-in-games design roundtable at Game Developer Conference raised a number of technical challenges the rest of us might not think of at first, such as the animation overhead of designing for a wide range of human sexual behavior.
From a CNET story:
I think the developers need to realize that while straight guys might seem to be the largest market segment for their virtual worlds, it's not the size that matters: it's the willingness. Those of us whose sexualities don't fit a simplistic marketing descriptor (like "straight young guys will always pay for sex" which btw isn't true either) might be more likely to try out an erotic metaverse than the vast but overwhelmed-with-options straight young guy population.