Tom Jacobs reviews research on high heels. A recent study's findings:
[H]igh heels exaggerate the differences in the ways men and women walk, making the wearer appear more feminine. This stimulates "sexual arousal in males," as well as increased attentiveness on the part of women who are scoping out potential competitors for male attention. This can happen on either a conscious or an unconscious level, but this evidence suggests the dynamic is real, and transcends fashion fads.