I'm as big of a proponent for remote workers as anyone (I basically quit my last job over it), but it makes a lot of sense for yahoo in this case.
1. They're regrouping, reorganizing and refocusing their vision. All of which are much easier to do in person.
2. The group buy-in that she needs to shift Yahoo's culture, product and focus is much easier to get when they're all in one centralized location.
3. Remote workers count for a fraction of their workforce? It's not like it's going to be a massive change for 50%+ of their workforce. They're just getting the few remoters back in house.
Like I said, I'm a big proponent of remote working, but this seems a little overblown to me.