There are a lot of scams on Facebook that we've warned you about in the past, and most of them can be used for like-farming. A popular one, for example, is posts that ask you to like or share so you can win something. This happens especially whenever Apple launches a new iPhone or iPad.
You might have seen recently during the huge Powerball frenzy people posting on Facebook saying anyone who likes their post will get a share of their winnings. How real do you think those were?
What about brain teaser posts, such as the ones that have you like or share if you can read the words backwards or solved a tricky math problem.
It isn't just posts either; it can also be pages. A scammer might set up a page for "I love puppies" or what appears to be a worthy company or organization. It puts up enough content to get a lot of likes, then switches the content for spam and scams. Once you've liked the page, everything new the scammers put up goes on your News Feed, and in some cases your friends' feeds as well.
Your best bet is to be very judicious about what you like and share on Facebook. Don't just reflexively click "like" on everything.
Take a look at where the post is coming from. If it's from someone you don't recognize, it could be a friend of a friend or it could be a complete stranger. It would be good to find out.
Notice the content and whether it promises anything for liking or sharing. If it does, it's a good clue that it's a scam of some kind. The same goes if you feel pushed or pressured into clicking like or share. You should also familiarize yourself with Facebook scams in general so you know what to look for.
Don't forget that, in the end, not liking things isn't just a good security measure. It also reduces the clutter from you in your friends' news feeds, and their clutter in yours, so you can all spend more time seeing the really important posts. That's a win-win for everyone.