In a recent interview by Garrett French, Marissa Mayer, the Director of Consumer Web Products at Google, was asked, "What should people do if their sites were totally dumped from Google?"
Mayer responded, "If you dropped in rankings, go back and look at who you linked to and who's linking to you. If any of these people are using spam techniques, they're the reason your site no longer appears on Google."
The phrase "who's linking to you" is particularly eye catching. Web masters have little or no control over who links to their web pages. It can be concluded from Mayer's comments that a hostile web master could sabotage the search rankings of a competing page by a practice now known as "Link Bombing".
Link Bomb - A collection of web pages containing easily detectable methods of artificially increasing web ranking, created with the intention of getting the targeted site penalized or de-listed by search engines.
In the context of search engines, spamdexing is the attempt at exploiting a search engines ranking algorithm so that a web page may appear higher in certain search results. Attempts at spamming range from the primitive (keyword repetition) to the sophisticated (link farming).
To assure quality, search engines have developed a myriad of techniques at detecting spamdexing and tend to automatically penalize web pages that participate in spamming. Penalization could range from lowering the rank of web page for certain keywords to removal from the index altogether.
Meyer's interview strongly implies that this automated penalization could be manipulated by hostile parties to target innocent sites. These parties could create multiple pages with very easily detectable spamdexing techniques and, from each of those pages, link to the site they wish to remove from the index. When the search engine detects the spamming, it penalizes all offending sites - including the site being linked to.
French responded to this train of logic in a follow-up article entitled What Did Google Mean? French is unable to get clarification from Meyer, so he and SearchEngineWatch editor Danny Sullivan conjecture that the true meaning of Meyer's statement is much less malignant than it potentially implies.
The interpretations of French and Sullivan are far from comforting as the possibility of link bombing is never discounted. Further, Meyer could have been exactly conveying Google's policy, and Google could have overlooked the ramifications of such a policy. Finally, other search engines - not just Google - could be susceptible to these tactics.
If link bombs can be set up, a question arises: which sites are susceptible to link bombs? Is it easier to link bomb smaller sites (eg. sites which are not deemed as "popular" by a search engine's algorithms), or is any site fair game? Could the Google site itself be link bombed so that it won't appear in its own index?
Link bombing is, at this point, a hypothetical scenario. The author has seen little evidence that it exists. However, the potential for its existence is unnerving as targeted web pages would be defenseless against such an attack.