Answer by Jimmy Wales:
I'm not yet completely to the bottom of it, but I can tell you this:
1. There was no systematic decision by admins or regular users that this should happen, and there has been overwhelming opposition to it. As is often the case, the mainstream media reports that "Wikipedia did X" in a fashion that leads people to think that there was an actual centralized (or even democratic) decision to do X, when what actually happened was the actions of one or two people, unnoticed by others.
2. There are claims that some women were mis-categorized due to the haphazard way that categories are handled.
3. There have been claims that a single editor recently went on a mass-moving spree but only as part one of a plan to move all authors from the general category to a 'male' and 'female' category. I haven't yet confirmed this, and I would oppose it. But it's important to note that if true, the motive wasn't sexism; rather, there was a foolish first move under way that gave an incorrect appearance.
4. I strongly support banning any editor who would do something like this and not apologize for the error.