Assume all data entered on this site (including your user name and IP address) is available for everybody to see. If you do not want your details made public do not submit them to this site, as it is open to the riggers on "the net". ie search engine spiders, mail spiders, naughty people on the net, etc etc...
You never need to register here at all. But if you edit here without logging in, everybody can see your IP in the RecentChanges page, if you create a username, only our server log will see your IP. If you want, use Tor to also hide your IP from us. Giving us an email adress is not necessary, or feel free to use mytrashmail.com or something.
Never upload pictures showing other people without asking them first. Never post private details, query logs, realnames etc, without asking. Before, not afterwards. I never feel like having to delete pages including their complete history.
see also: Privacy