The scammers may also send fraudulent messages claiming that their potential victims are so-called lottery winners and they need to send money in order to claim their prizes.
The Facebook "Share Now" and "Pick Me" Gift Cards and Cash Scam

I will choose people randomly on Facebook everyone who *shares* will receive gift cards, cash, and big winners can win cars & homes "Share now" don't miss!!! We watch Until the weekend!!!
I will choose 900 lucky people. $90,000,000;- each only follows instructions. ...
Step 1 - like
Step 2 - Share
Step 3 - comment "Pick Me"
Also, if you have received a message stating Facebook will donate money to a child if you like, share or comment on some content, please do not follow the instructions in the message, instead, report it to Facebook. And, if you have already commented on Facebook posts with sick, starving and injured children, adults or animals that you are not able to determine the legitimacy of, please click here for instructions on how to remove those posts from your Facebook Wall and Timeline.