This is not really cheating, it is part of the rules in correspondance chess: If your opponent does not move within the alotted time they lose.
You should only report it, if you believe that he has setup these accounts on his own in order to boost his rating.
Also note, that if your opponents time out after only one move, you do not get a higher rating because of it.
I have been playing a game here with another guy. This guy, has kept playing me until the end, when it was evident many moves before that he had lost the game. Not too kind, but it's ok, is his right to play until the end. I just took a look at his profile to see if he did this only to me or if it was part of his usual behaviour here. And I saw that he had more games in similar conditions to mine. Today, finally, i checkmated him, and took a look at his profile again. To my surprise, I see that this guy has recently won 4 games on time with new users who played his first game here and that made only one move in each game. Easy and nasty way to keep your rating while you are loosing real games. To whom should I report this?