Otherwise known as Unsolicited Commercial Email (less frequently, unsolicited commercial postings to newsgroups, weblog comment forms, and even wikis). Pretty much anything you get Emailled against your will. This is a bad habit and should stop.
NewZealand is currently considering LegislatingAgainstSpam. WLUG is considering putting in a submission based on the discussion on that page.
Some things that are related to Spam:
Things that aren't really related to spam:
lib/CachedMarkup.php (In template 'browse' < 'body' < 'html'):499: Notice: Only variables should be assigned by reference