When a person gets "clickjacked" it means that they clicked on a suspicious link (usually on facebook). After they click on the link, their account becomes infected with malware. That malware tends to spam the hell out of their friends by posting more malware laden links on their friends' walls.
Paula's wall: Like OMG, you guys! Dell is giving away FREE computers! Click on this link (malware-laden link) to get a FREE computer! It won't last long! CLICK on the link right now!! =)
The same message gets posted on all of her friends' walls.
Paula's wall 2 hours later: Wow, somebody totally hacked my account! I did NOT post all of that crap! I'm changing my password!
Paula's friend: Paula, you are such moron! You didn't get hacked! You got clickjacked! Stop clicking on those damned links!