How Women Pick Mates vs. Flings

http://www.livescience.com/humanbiology/070102_facial_features.html

Women seem to judge potential mates by how masculine their features are, new research shows. Men with square jaws and well-defined brow ridges are seen as good short-term partners, while those with more feminine traits such as a rounder face and fuller lips are perceived as better long-term mates.

yeah, i would definitely fall under the latter category there.  never had problems finding girlfriends, but flings have always eluded me.