I see a ton of people complaining(rightfully so) about getting blank RSVPs back. I get it, like how hard is it to write your name people!!! However, can't you just print out small return labels for the RSVP cards with name and address of the guests on them? Is there something wrong with this concept?
ETA: I know you can also use invisible ink or number the cards...this just seems like the obvious answer to me...unless there's some big reason not to do it.