You can't have sex when you're dead (even though people can still have sex with you).

From IMDB's news page:

The revelation by Sex and the City's costar Cynthia Nixon that one of the principal characters will die in the theatrical version, due out on May 30, has touched off a wildfire of speculation on Internet blogs about who the character will be. Rumors that a character would be killed off had been circulating for months. When asked about them at the ShoWest convention in Las Vegas last month, another costar, Sarah Jessica Parker, predicted that people will be "very surprised" by what they see on screen. "There's a seriousness about something that happens in this movie," she added, without directly responding to the question. She added that she thought that writer-director Michael Patrick King "wrote the role of a lifetime for me." Bloggers have speculated about each of the female leads as well as Mr. Big.

Or maybe they all get stomped into the ground by the monster from Cloverfield. I guess we'll find out this summer.