I stumbled across this on ZDNet (so... this isn't some weird email whoosie going around):
http://news.zdnet.com/2424-1009_22-213604.html -- it says in part:
On Wednesday, the FBI and its partner, the Internet Crime Complaint Center (IC3), warned against a new email campaign being used by the creators of the Storm worm botnet.
The email uses the phrase 'FBI vs. Facebook' in its subject line and contains a link to view an article about the FBI and Facebook, the popular social-networking website. Clicking on the link downloads malicious software onto the victim's computer.
I've already rec'd this email in my spambox several times and just deleted... but wanted to pass it on. I double checked it with Snopes, being naturally skeptical, and it's real: http://www.snopes.com/computer/virus/fbi-facebook.asp