A little while back, I referred to these phenomena as extremely simplified forms of social networks.
Just read something that I think betters that description.
Forums: The grandmother of the blog. The online forum is the genesis of social media, connecting users to each other online before blogging was even a twinkle on the horizon. But just because they’ve been around for a long time doesn’t mean they’re outdated. The Twitter social networking system is largely considered the forum of the future, combining the traditional online forum, a blog and an instant messaging system.
(Source: Corporate Writer & Editor, Feb 2008 issue – sorry can’t link to it directly as this is not freely available content)
I think actually that you can strip the reference to blogs out and the description wouldn’t suffer. & the reference to IM is (I think) mostly about the user interface angle – when interacting with Twitter et al, it works best from a little desktop app rather than from the browser.
But in terms of content, it does seem like the good ol’ forum is what Twitter etc. most resembles. Lots of chatter, some goofing around, cool links. And due to the extremely limited number of characters per post, the main drawback of old-school forums has been largely eliminated: those longwinded and annoying rants from unhappy campers that flit around the edges of every online community… ;+)
Twitter = evolved message boards, or Forums 2.0.
Seems like a useful way of thinking about it. Gonna mull that one a while.