To me, the best erotica comes from writers' own experiences and desires. A lot of erotica comes purely from writers' fantasies, but stories can lack impact if the author doesn't bring some of her own experience along with all the research.

And here's the thing: no one thinks if I write about a murder that I've actually murdered anyone, but most of my erotica readers will assume I've experienced what I'm writing about even if I haven't. (Although I do write mostly from experience.)