One might think from the runaway success of the books, and the huge interest in the movie, that the suburban moms who are supposedly the target market are sex-starved porn fans. Or that they have lost their ability to distinguish good (or even adequate) writing from "Oh jeez, my inner goddess is doing the merengue while she bites her lip, triple crap."
Actually, I believe 50 Shades taps into our deepest darkest fantasy - of someone else making decisions and doing the planning for at least a few hours. And for that we will put up with lousy writing, a hero who is more of an abuser than a fun BDSM devote, and sex scenes that aren't very sexy. At least someone else planned them for us!