They've been a legal gray area since they were created. We've always known that the Government would get into regulating them someday, but nobody knew what form that regulation would take. They could be all but ignored or they could do their level best to squash it like a bug. I believe this is a good sign in that it seems to be pretty light regulation and provides some security - the more official recognition Bitcoin gets, the less likely the Government is to try to crush it.