I can't speak to Facebook, but it is pretty well known that the Fed gov has people monitoring websites that they feel are a threat to America..including what are thought to be "Patriot" sites, 2nd ammendent sites, survival sites, and alot more...
I belong to a site that has been monitored and the owner of the site has been contacted my "Big Sis's" Department of Homeland Security and demanded contact info for members because of their postings....he is the kind of guy that told them to pound sand...