SEO, or search engine optimization, is the art of optimizing Web sites to appear prominently in search results lists when relevant keywords are searched.
Blackhat SEO tries to do the same thing while flouting search engine guidelines about acceptable practices, such as prohibitions on the deceptive use of text or page elements. Blackhat SEO may also try a parasitic approach, by embedding malicious code in someone else's well-ranked Web page and redirecting the visitor without notice or permission.
In the case of Google Wave, search terms such as "google wave demo video" and "google wave invitation" have recently produced lists of search results which include malicious Web sites that have gamed Google's PageRank system to appear prominently.
Google knows that cybercriminals track popular search terms religiously so they can use those terms to hijack searchers. And it watches closely over its index using automated and manual methods to remove links leading to malicious sites. Chances are that the sites spotted by Websense have already been removed by Google. But it's almost always playing catch-up.
If there's a lesson here, it's temper your enthusiasm with some wariness. Chances are that you'll find some unpleasant surprises when using popular search terms.