The term "Google bowling" has been floating around the Internet for a while now. The practice is one of many that can be put under the heading of negative SEO, and while I'm not a proponent of these methods, they are worth noting:
Google bowling: As Google attempted to curb link-popularity exploitation by penalizing Web sites that purchase link ads across the entire site, it also created the environment in which Google bowling came to be. As a form of negative SEO (search engine optimization), certain unscrupulous entities began buying sitewide links for competitor sites, thus causing them to incur the Google penalty. Simple, evil and a very real practice.
Spam in another's name: This form of negative SEO is even more simple. If spam gets Web sites in trouble with search engines, then creating spam on behalf of a competitor might lower their search engine results. In addition, a Web site's URL can be used for spamming in online forums, social-network sites and blog comments. It's hard to prove that the victim is innocent, and social-network sites might ban that Web site regardless. This can have a negative effect on the link neighborhood of a site.
Tattletaling: Did you buy links on other Web sites to improve your search engine rankings? Google doesn't like that at all. If your competitor finds out that you use paid links, he might tell Google and your rankings might drop! Of course, you can tell on your competitor, too.
Faux copyright complaint: If a search engine is notified that a copyright infringement exists (or might exist) on a Web site, then the search engine must remove the reported page from its index for 10 days. Snarky, but effective if someone wants a page out of the search engine results page (SERP) system for a spell.
Faux duplicate content: If someone creates duplicates of a competitor's Web pages, these duplicate pages will split rankings with those of the original site. Again, this isn't theory. This is something that is done in practice regularly.
To be clear, I am NOT promoting these tactics, and some of them will put you in legal hot water. But it is good to be aware of them so you can protect yourself against such practices, or at least identify these attacks when they are occurring. And, if someone is pulling one of these stunts on you--well, all's fair in love and war.
Hat tip to Axandra for these tactics.