Several times in the past month I have been told anecdotes about women academics who made carer decisions that annoyed other people. In some cases the annoyance was justified (e.g., women who reneged on a commitment in an unprofessional way), in other cases not (e.g. women who left one university for a better offer at another).
I suppose it is because there are still so few female science professors that each woman's controversial decision is seen as a Poor Reflection on All Women. It would of course be absurd to extrapolate one man's decision to move to another university as somehow indicating anything about the reliability or loyalty of men in general, but somehow a similar move for a woman is seen by some in a different way.
For men, the response might be "He must be really good if that other university hired him away." For women, the responses I heard recently about one woman who changed jobs were: "She really left her (first) university in the lurch", "She's so selfish, all she cares about is making more money", and "That's what happens when you hire women. They leave."
And if a woman makes an apparently 'unprofessional' decision, such as backing out of a commitment at the last minute because she doesn't want to move so far away from her boyfriend, this is seen as a setback for all women, eliciting responses such as "That's the last time that department/unit/professor will try to hire a woman."
This is another reason why we need more women in science -- so that some women can screw up and it isn't seen as a Poor Reflection on All Women. And other women can make career decisions to change universities and have those decisions seen as reflecting excellence, not selfishness.
9 months ago