Have you ever heard of "like-farming"? This is a new type of scam that has taken over many users' Facebook feeds, that begins with spreading a potentially positive message and then uses all the "likes" to spread computer malware or gather users' personal information.
How does it work?
Once a particular post or page gets a sufficiently large amount of likes, a "like-farmer" will replace the content with something that can steal the personal information from the "liker," or with a link that can spread viruses and malware to whoever clicks on it. This usually happens after a piece of content goes "viral," so that the scam hits a large number of people.
What do these posts look like?
Often, these posts will be inspirational messages: "Share if you want your friends to have a great week!" for example, or "Share if you want to help this little girl with cancer." These are posts that can quickly go viral due to the good intentions of Facebook users, but can be quickly converted into malware-spreading links.
Here's a bit more information about these scams, via Consumer Affairs: bit.ly/1KXke49