there needs to be a feature for at least having them opt out of the site.
here is my friends issue. he has a forum about business opportunities. he makes his money off the forum via advertising like banners and text ads, but his biggest seller is email solo ads. he has over 20k members which have been members of the forum since 2006, some have forgotten they ever signed up, or possibly their email account was deleted and then recreated by another person who in turn gets emails.
his rules are clear on his site before they join that they WILL get advertisements if they join, if they do not want to receive those ads, then do not join, its posted above the signup form, on the rules page and in the tos which they much checkmark before joining. but he still gets the odd person who yells at him or reports his emails as spam and to delete them from his forum.
he ended up making a thread to have people post if they wanted to be removed.
Like something like facebook or other membership sites they all have the option to delete their account under user profile. as it should be up to the member to do it not the admin. what if a persons email addy was hijacked and they requested it to be deleted, he deletes it but then finds out it was not a real request...
So definitely a feature that needs to added for at least allowing them to deactivate their account.
It would also be nice to see a bounce manager or list cleaner to verify all email addresses to ensure all accounts are still valid.