It works, but you have to be VERY selective in the type of posters you're wanting. Most posters will only post things like "what's your favorite color", "guess my wait", and the like. There are a lot of non-english speaking accounts, and the seldom post about the topic your forum is about.
I suppose it could be useful, if you're conditions for posting are clear, and posters follow them.
Trying searching on this site for postloop, lot of information and stories about it.