I agree with you about how broadly the word "bisexual" is used these days. The Merriam-Webster dictionary is a bit vague...

Main Entry: bi·sex·u·al
Pronunciation: (")bI-'sek-sh(&-)w&l, -sh&l
Function: adjective
Date: 1824
1 a : possessing characters of both sexes : HERMAPHRODITIC b : sexually oriented toward both sexes
2 : of, relating to, or involving both sexes

"Sexually oriented toward both sexes" could simply mean sexually attracted to both sexes. That could be a determining factor of the validity of some bisexual claims. I mean, a lot of women would like to present themselves as bisexual, and might even find other women entrancing and beautiful, touchable and kissable... but other women don't really make them wet their panties. I'd say you have to want more than a pleasant little make-out session if you're truly bisexual.

I don't think a desire for a long-term sort of relationship with people of either sex is necessary for someone to be considered bisexual. It isn't necessary for a person in a hetero relationship to want a long-term relationship in order to considered a sexual person. I believe I've had actual mini-crushes on a one or two women, and back then I was able to see myself wanting to be with those women in a long-term sort of relationship if they felt the same about me and it came to that. (They didn't, and it didn't.) But I have never labelled myself bisexual. I've said psuedo-bi, or that I have some tendencies...

I think the main difference between the poser and the bi-curious and the real bisexual woman is whose fantasies they are acting upon. If they are acting in a bisexual manner for their own direct pleasure, they are more of a genuine bisexual than those who are acting that way mainly for the pleasure of others or for indirect pleasure through other people's pleasure.