How can they be "actual addresses" if they are also fraudulent addresses on the other side of the State?

I guess what you are saying is that Acorn got hold of a Republican voter database somehow, then re-registered all the Republicans with fake addresses. Then the State will process the registrations without checking them, and when the Republicans go to the polls, they will find out they can't vote.

This doesn't strike me as a very likely conspiracy. It is bound to be discovered, even if the bogus registrations managed to get through the system. The people who turn up en masse at the polls and find they can't vote can simply ask for a proxy vote, and their vote will be counted later when it is all sorted out. The management of Acorn would certainly go to jail.

I prefer the simpler explanation that this was lazy employees trying to claim extra hours on the job.