If you previously registered an account but never got the email, or never figured out how to complete the verification process (it was broken for a while), those accounts (roughly 3,000 of them) are now deleted, so you can try to register again.
98.72% of people who use this service don’t need to register. It’s a mystery why people register – then don’t do the things that require registration – creating a poll, entering a factoid, setting a topic for a show, saving favorites, etc… I guess people just like to join stuff.
If the registration bounces because the email address is fake, it was rejected as spam, your mailbox is full, etc within a few days, the invalidated account will vanish.
Similarly, if you ask to be a volunteer, but never send the email requested by the process, your request will be deleted after a few days.