Spamvertising

Spamvertising is the practice of vandalizing wikis and blogs in order to get a higher page rank for the vandal's website.

Spamvertisers insert links to their pages (typically, sites purporting to sell some commercial product) and add their favorite keywords. After a little while they hope that Google or some other search engine will find the vandalized page which should then give that page a higher rank when searching for the spammy keywords.