Since a few minutes Google SERP pages have become completely unusable. Any result is flagged with the This site may harm your computer warning message, it doesn't matter which query are you searching for.
Here's a screenshot.
Funny enough, Google also flagged itself as potentially harmful.
I suppose the problem to be caused by a really weird bug. Changing browser or logging out from your Google Account doesn't matter, thus I guess this bug should affect a really wide range of users.
Update: A thread is available at the Google Blogoscoped forum, #googmayharm can be used to track conversation on Twitter.