Listed below is an example of things going a little awry for Agency FAQS. With the kind of warning, even I was wondering if it was safe to venture on to the site and I have been using the site for ages.
This is a simple search result, notice the RED.
The process being followed by Google or Yahoo is not clear yet, as neither has published its classification technology, which makes it difficult to determine how alike the two services are. The one visible difference is the prominence of the warning in case of Yahoo, while on Google; you do get a text link “This site may be harmful to your computer”.
The service makes a lot of sense for the user and will prompt the site-owners to clean up their acts or be listed “harmful to search”.