When you post to Facebook you're giving information to not only those on your friends list, you're giving it to Facebook.  And they're going to give that information away to anyone they want.

Facebook has teamed with Politico in an information sharing agreement.  Any post that references political candidates will now automatically feed into a sentiment analysis tool that spits out anonymized information to Politico.  They will use the information as they see fit.  Mainly for analysis but also as fodder for their stories.

Facebook expects you to be placated by claiming none of Facebook's employees will be reading these posts.