I want to coin a new term: Casual Social Network as an analogy to Casual Games.
Same kind of setup: Social networks that
  • don't require you to commit to an immersive experience
  • can be used casually in short bursts
  • don't require you to learn the complex rules of a new universe
  • don't ask you to nurture yet another online identity
  • make lurking easy and non-suspect.

In short, social networks you can use just like you use casual games.

Examples and Counterexamples

Blogging is a sort of distributed casual social network - or I should say, blog commenting is.
Usenet is very much a casual social network
Forums are often casual social networks
IRC channels are often casual social networks

The recent spate of Social Silos work as casual social network to varying degrees. Flickr used to be an excellent casual social network - but the shift to Yahoo IDs has completely destroyed that and turned Flickr into a silo outright. A silo with universal read access, but still a silo.

Facebook and Myspace are not casual social networks - but Myspace is more so.
Facebook applications (under the F8 platform) could be seen as examples, relative to Facebook proper. Since the social investment was already made when signing up to Facebook, facebook apps are - on the surface at least - friction free. With the kind of access Facebook provides to your social data, they can accrue social transactional costs in spades, though. But clearly, this is the Facebook play - that the apps can be used casually like this.

World of Warcraft and Second Life are the antithesis of casual social networks.
Del.icio.us is a good example of a service that's very casual, but the social effects of del.icio.us are so public that it's a good question if its a network at all.

The World Needs More Casual Social Networks

I think this term maybe captures better what I'm going for with the Public Digital Spaces idea - or maybe casual social networks are the next step up the ladder from a public digital space. It's the difference between a genuinly public space (an open square, the public library) and that bar where the bartender knows your favourite drink - but still a while away from actually paying club dues at the golf course.

Identity in casual social networks

Your identity in a casual social network is limited to the social network. The characteristic distinguishing feature is that you're known only by your handle on the network and nothing else - to the extent that your peers within the network have more social data about you they have so through other channels.

Participation in these networks is never always-on, but instead mostly just occasional.