Does your third place move? Do you find yourself spending more time in one place than another which shifts over time?
I find the place where I spend much of my time on the web changes with time. I get interested in one place and they find that the action is better at another place. Then, I find myself spending more time there. Services like Twitter and Facebook let you link your places, but I find myself spending more time in on than the other (e.g. checking posts, etc.). It's sort of like owning a Recreational Vehicle and picking up every so often to move to a new park. The basics remain the same, but the scenery changes.