I think they are different. Facebook can be a 'dangerous' place, where a person's profile can be hacked. Also, you cannot write long passages or topics. Good thing is that you can restrict what you write to only friends. In Hubpages, everything is open, and you can participate as long as you are a hubber. Of course, in Hubpages you can write your hubs and publish as many as you wish. The forums also give a good platform to interact.