Haven't noticed it here. You can count the number of active female bass players here (4 county area) on a half a hand (sorry ladies, having a bass in the closet you "used" to play does not make you an active bass player. Dust that thing off!).
Female lead guitar players? I know of none gigging. I'm not counting singer/players, they're all chording. Know a couple of those gigging

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The reason for the increase IMHO is pure numbers. Looks like women are, lets say, 5% of the musical rock force (players, not singers). I *have* noticed an increase in the number of bands/ players, etc lately.... so if women are 5%, and the number of total players goes up, makes sense you'd see a few more out there.
And there really aren't that many female role models for young girls in the rock world. Most of them that are publicized are lauded for their looks. Unfortuantly, overweight/wrinkled/balding women have a heck of a lot harder time finding acceptance as players than men. Face it guys, you judge by looks first.

Until we get some female executives in the higher ranks, the not so good lookers will be pushed aside unless they are 300% better than the competition.
Oh, and the guitar center comment.......no it doesn't have a "Men Only" sign above the door. However, I've met many salesMEN (had to point that out, never seen a woman working there) who have that mentality. A woman picking up the bass or guitar gets a "how cute" reaction. If she doesn't start shredding immediatly, everyone just gives her an awwwwww look. That said, I have met a few salesmen at gc who treat me like a player versus a woman, and guess who I get to ring me up (they are commissioned). Man, I could give a whole course on how to treat female customers at a music store. Hint #1: if they are eying 5 string basses, chances are good they are players and you shouldn't be condescending to them.....
BTW, how about some youtube links of women players ya'll respect?