Github did have a bug and noone knowledgeable about Rails appears to have made even a cursory inspection of the security of their controllers - which is where attribute protection actually belongs, since different controllers and different users change different attributes. Protected attributes is a blunt tool for simple situations, which is why it's not enabled by default. Github had a pretty terrible bug, discovered, and fixed it. They may not have handled it perfectly, but the certainly don't deserve this sort of mon hatred - any competitor you go to is likely to have security flaws as well, perhaps more severe and subtle.
@homako didn't just expose the bug in github, he exploited it to make an unauthorized commit to Rails master. His account most certainly should have been at least temporarily suspended as GitHub had no idea what else he might do to prove his point.
So basically, most of the comments here are glaringly wrong or ignorant bandwagoning, and it makes me wonder about the accuracy of information here about topics I'm less familiar with. A sad day when you realize all this intelligent discussion you thought you'd been reading about new topics was probably just grandstanding by eloquent fools.