A Facebook virus scam is going around:

"The phrase 'Facebook Fan Check Virus' is currently a hot trending topic on Google, with many net users searching for information. However, hackers have set up websites pretending to be about the 'Facebook Fan Check Virus,' but which really host fake anti-virus software which display bogus warnings about the security of your computer in an attempt to get you to install fraudulent software and cough-up your credit card details,"
Article is here: