Facebook has close to a billion users, which makes it a prime target of scammers and spammers who simply have nothing better to do with their time.
These "share" and "like" scams have been around for quite a while now, where pictures of sick people, most of them children, are the main focus of the posts. The text accompanying the picture usually includes a sob story, followed by fake claim: that Facebook will be providing medical aid and assistance to the subjects of the photo, provided it reaches a specific number of likes and shares.
These are all scams, of course. Facebook doesn't extend any sort of financial aid to campaigns such as these, so you'd only be wasting your time spreading the word about the photos. Here's an example of the text included in one such campaign:
She's suffering form cancer! Facebook has promised to give $1.20 Dollars on each share! Please, share and make it (sic).
Brett M. Christensen from Hoax Slayer explains that the only thing you'll be giving the people in the photo is grief--grief at having their photos stolen and spread in such manner where nobody ends up winning.
The cretin who created this hoax undoubtedly stole the child's picture and used it in the hoax message without the permission or knowledge of the little girl's parents or carers.
-- Brett M. Christensen from Hoax Slayer
Do everyone in your network a favor and think twice before hitting "Share" when you spot sad or pitiful pictures depicting some sort of child in need, because those campaigns are an absolute hoax.