We've had a bunch of new-user sign-ups where the account was activated but the person has never logged in. And some cases where they never activate. In some of these cases, if time goes by and it doesn't look like they're coming back, I may start suspending these accounts.
SMF forum recently had another security patch, and I'm wondering if some unscrupulous folks out there are trying to do nefarious deeds.
It looks like the server has also had an issue sending emails, so I'll track that down. It's needed for account activation.
EDIT: Note that I'm just talking about accounts that have never logged in. I'm not going to suspend real people who just haven't been on in a while.