Probably not one of the last, but likely one of the last with this format (and plans to continue in this format). I have found trying to hold a conversation on Facebook or Twitter is next to useless, as the format doesn't really allow for in-depth discussion. Of course, it seems most people that I've spoken with on Facebook don't want in-depth discussion, and much prefer the short, simple messages to longer, more involved conversations.
To me, Facebook feels like how you talk at work. TrekBBS, and message boards like her, feel like what you do at the bar. You walk in, sit down, order a drink, and then shoot the breeze with your buddies.
I much prefer message boards like this. My own message board is like this (it's not technically sci-fi, but more fantasy), and I have no intentions of changing that anytime in the near future.