This virus is an interesting one because of its success and mostly because of people insecurity. Anyway this virus was ingeniously created and it was build for the simple Internet users, probably it would have no impact on a user with little knowledge about threats.
This virus is a two part virus: First part is the one that intrigued me, it uses a technique called SQL Injection and it will compromise some Web Sites where the user will get a popup with a warning that his computer is infected and in order to scan a free software is available for that. That software is in fact a bait, but honestly I like the name Windows Stability Center (the Microsoft antivirus is called Microsoft Security Essentials) and I think that this name has tricked a lot of users. The fake antivirus will say that the computer is infected and it will require a full version for the computer to be cleaned and this is the part where your credit card kicks in.
At a point Apple Itunes (confirmation pending) web site was infected with this virus so it can affect a lot of companies and will redirect a lot o users that will spend money on a fake antivirus.
More about SQL injection http://en.wikipedia.org/wiki/SQL_injection
And a video about the virus where you can find more info about the infection: http://www.youtube.com/watch?v=wKI5dg1cs74&feature=player_embedded