Facebook is 'the' most popular application in the social networking space today.
It's a hit and people are loving it!

Like all other applications, this too has pitfalls!
The modus operandi is all too simple.
All of us have heard of such things before, but some people just don't care.

An external link is posted on a profile which is rather enticing in nature.
Gone are the days when a porn inspired quote got the attention of the users.
These days, the quotes are more sublime, docile and a bit funny.

The probability of people clicking on such links is very high.

For example,
"This boy fell straight on his face after this girl slapped him"

You have to 'like' this post to view the video.

Here comes the trick.
The like button is a new feature of FB which allows a developer to build a plugin.
Then the users profile details are accessed (ofcourse with permission, nobody's complaining!)

The code on the button click can be customized to show a thumbnail of a page, a picture and title of the page. This makes the trick more authentic.

Before you know, you are transported to a rogue page with malicious content which hooks the trojans on to your machine!

And to rub more salt on the wound, since you like it, it gets posted on your wall for other to see.
And one by one everyone 'likes' it!
This is like a virus which spreads systematically and nobody suspects because so many people 'like' it!

One way to tell the 'malicious like' from the 'normal like' could be that the malicious ones always appear like a button on mouse-over.
Something like this :
The normal ones are generally just like a hyper-link.

All I can say is... just be aware and do not let unknown rogue applications access your profile data.
Forget the people you are spreading you to, you are also, in the process risking your own laptop/desktop.

Some more example pictures(now this post obviously points to malicious content because of the tag line:-) ) :