I haven't figured out Twitter either but I have to disagree about Facebook. Groups and fan pages make Facebook one giant forum really. Want to discuss Doctor Who? Pop over to one of many Who fan groups. Want to talk about last night Grimm episode? There is a group for that too. Want to go hang out with local genre fans? Yeah, they have an event planned. AND you get to keep up on how Aunt Martha is doing after her hip surgery.
Forum paved the way and Facebook picked up the ball and ran with it.
I'm not so sure you're right here, but it depends on what portion of FB users are like the sort of people I encounter on the anandtech.com forums - I think that with some of the crap they spout, they're unlikely to do that if their real name was on the posts. Combine that with employers wanting to spy on their employees on FB, I think that adds quite a bit of weight as an opposing argument.
Also, FB is (IMO) generally regarded by a lot of people as "keep your political/religious opinions out of here", and is considered to be as 'light reading' rather than getting involved in some serious discussion about xyz. I generally adhere to that philosophy on FB as well because that's what my friends seem to do. As it shows up on one's feed where you've been posting on other FB-hosted resources (message boards, etc) by default, I don't think FB is going to wipe out forums.