We signed up with WPMU Dev at
http://premium.wpmudev.org in September and cancelled shortly after, within a couple of weeks.
I noticed today they had re-activated the membership and started charging the card again at the rate of $80 a month also issuing charges from another site called Buddydress.
So if you are considering signing up to WPMU Dev my advice is dont, or use a throw away prepaid credit card, because they cannot be trusted to handle your card details properly.