One of my absolute favorite posts by Dear Sugar:

"Whether you're into one night stands or not, a recent study shows that men and women engage in them with completely different intentions. Guys are interested in just one thing, the sex (what a surprise!), whereas women yearn for the feeling of being desired and needed. Of course, guys end up getting what they crave, but most women just end up feeling used and emotionally crushed. They have hopes that this one night of passion might turn into a lifetime of love and romance, but it's often a huge letdown because after that one night, they're no longer wanted.

When it comes to casual sex, women feel flattered that a guy is that interested, but according to Anne Campbell, a psychologist at Durham University in England, "What women don't seem to see is that men drop their standards massively for a one-night stand." She goes on to say that in fact, women shouldn't feel flattered at all just because a man wants to have sex with her one time."