Some floaters choose to post only on subjects where they might find agreement. For instance on a Clinton is God or Clinton is Dog thread you won't find anyone outside of the DU or FR domain. But gun control, abortion, etc. the hot spots where both sides have internal disagreements, you will find more posters that may or may not really be for the site. After awhile you can spot who is who.
Some floaters have been known to take an absolute extreme position (left or right) in order to bait others into looking more extreme than they really are.
I posted at DU for awhile (banned for calling a european socialist "anti-american"). Basically arguing with hard core socialists and standing with the few brave DUer's who are for the 2nd amendment and fight the gun grabbers constantly. There are a few reasonable people there but not many.