Many women grow up with a sense of physical
vulnerability that's hard for men to appreciate. Our
culture's relentless treatment of women as objects
teaches them that they are defined by the one thing
that men around them want from them—men who are
usually bigger, stronger, and (like any human)
occasionally crazy. This feeling—often confirmed by
actual experiences of harassment and assault—can lead,
understandably, to a lifetime of low-level wariness
and sense of vulnerability that men have trouble
appreciating.
This is so absolutely dead right on the money, I find myself wondering where a male author gets such an insight. I feel this way, and I was raised in idyllic suburban circumstances surrounded by loving and honorable men.
(Edit: Here's an old comment of mine on the phenomenon of women preferring gender anonymity online: http://news.ycombinator.com/item?id=750413 )