[QUOTE]Roger Thompson of Exploit Security Labs posted today about finding poisoned Google sponsored links that surreptitiously direct searchers through malicious sites that attempt to surreptitiously install malware on your PC…
[/quote]
http://blogs.pcworld.com/staffblog/archives/004213.html
The black hats have also been buying google search words for some considerable time and probably the same for other search engines that sell search words/terms.
Another reason for a good resident antivirus, good antispywares (at least on-demand) and use Finjan or SiteAdvisor to scan the links showed in the search page.