(I didn't think that was illegal if you were in the same district, but edited it anyway)
It is, and it is (I thought?) common knowledge due to the high profile cases where this was abused. There's nothing morally wrong about doing it, but it is illegal and people do face consequences for it.
Hm. So how do homeless people register to vote? Can I register in the same way? Cursory Google search seems to indicate you only need a mailing address, and your residence can be described as a cross street or some such.
I mean, I don't care if the government knows where I live, but I do care if they leak it to people without my explicit consent.