Websense, a computer security firm. has just released a new report that includes a brief discussion about the use of web engines to spread malware. You can read about the report in the vnunet.com article: Hackers 'poison' search engine results.
[We] believe that an increase in 'poisoning' search results and DNS servers from the most popular search engines is possible," said report author Dan Hubbard, senior director at Websense.
"In this scenario, attackers ensure that their sites appear high in the return lists of queries. When users visit those sites, they are infected. For example, in a search for anti-spyware a list of sites infected with spyware might actually top the list."
If you would like to read the full text of the report, it's available here.