DERPY SHITSTORM, ROUND 2!People are blowing this way out of proportion. I mean, to like fantastically fucking stupid levels.
I'm upset about it too, but I'm not about to raise a pitchfork and go bray on Hasbro's doors until it's fixed or I'm heard. That's stupid. People need to stop a moment, chill the hell out, and think for a minute before mindlessly foaming at the mouth like an enraged zealot.
I do remember talk in the past of the name "Derpy" being registered to a character, and that using said name officially might lead to legal problems. If I were to wager a guess, that's probably why they changed it. I would have too if I were in their shoes. All they're doing is watching their own asses. And I can understand why. Their PR department doesn't need that kind of hit and I wouldn't want them to.
=EDIT: So it turns out that the actual reason may have in fact been because of the crying people did about her making fun of disabled people. (Read this! http://kreoss.deviantart.com/journal/Derpy-287023334)