mpj220 et al,
I have it from Marc himself that all you have to do is not visit RCU for 30 days, and your account is automatically deleted. You can also have your account manually deleted by an administrator by simply requesting it. It'll happen as soon as they're not running around like decapitated chickens, putting out fires.
RCGroups, the site that's "going to take over," the site that's "the standard by which all others are judged," does NOT have a way to unregister yourself at this time, either. I've personally confirmed this. Torqueroll? Same story from what I'm told. I don't know, I don't like what torqueroll did to the layout.
Also, ad rates are based on clicks, not membership numbers. This information is from Nathan, one of the administrators. These guys are under close scrutiny, and they'd be in deep doo-doo business-wise if caught in a lie right now, so they have every incentive to be upfront and truthful about site policies.
Sorry to see y'all go, but I hope this information helps.