From SOPHOS:
Right now we're seeing a significant number of Facebook users posting messages such as:
OMG OMG OMG... I can't believe this actually works! Now you really can see who views your profile!!! WOAH
and
See who views your Facebook profile in real-time!!!
If you make the mistake of clicking on the link to one of these pages offering to tell you who is viewing your Facebook profile, you will find that the people behind the "services" want you to do a few things first.
For instance, they'll ask you to "Like" their pages (which means you are spreading the link to friends in your social network), and they will ask you to advertise their site by posting an "OMG" message (with a link) to at least five different places on Facebook.
After all that hard work you would hope that they would give you access to the powerful Profile Spy app wouldn't you? But I'm afraid your luck is out.
They'll next ask you to hand over your personal information by taking numerous surveys - before ultimately trying to trick you into handing over your cellphone number which they'll sign up to an expensive premium rate service.
Complete Article:
http://www.sophos.com/blogs/gc/g/2010/07/23/viewed-facebook-profile-care/