Can there be a "Wikepedia reserve army" list where anybody that hasn't been seen in 90 days is listed. To get back on the main list, one simple log-in would do the trick. I would not object to seeing a lot of "accidental" registrations cancelled completely; many of these people have probably even forgotten that Wikipedia exists. They can always re-register if they want.
There might also be cases of people who come to Wikipedia, register, forget about it, then return a few months later, and completely forgot their password, maybe even their registration name, and re-register under another name.
Andre Engels