Google is alerting users that their computer is infected
Credit to Brian Krebs: http://krebsonsecurity.com/2011/07/google-your-computer-appears-to-be-infected/
I admit to feeling some concern about this tactic. The bad guys themselves use scary warnings to social engineer users into installing fake security software. How is the User going to differentiate between a fake scary warning and a real one?
And I fear it is only a matter of time before the bad guys find a way to replicate the Google alert, except the “Learn how to fix this” link would expose the user to something more malicious.