In shockingly Germanic fashion, Facebook has gifted an entirely new verb to the English-speaking world. What do you do if you choose to 'like' someone's comment, link, photo or whatever, and then change your mind? Of course: you opt to unlike it. (Facebook doesn't grant you the chance to go as far as disliking it, but then I guess you simply opt to hide people you don't want to see).
It strikes me that we will need many such new verbs in the future. How else will we prevent our society gradually moving towards the ultimate synoptical inter-connection of every digital node in the world? How to tackle all the social pollution that's arising? Hence we need more mechanisms and norms to untag, unfriend, unlike, unsend, unreceive, untwitter...
You could look at this as just another example of privacy technologies in action. I've long believed that breaks in informational networks are just as valuable as links (I mean that culturally and politically, but if you prefer an economic explanation read Ronald Burt's paper [pdf] on this). Privacy is one way of understanding the value of disconnects. But things are more complicated than that now. 'Private' sits in opposition to 'public', in parallel to how 'economic' sits in opposition to 'political'. But can all efforts to unconnect really be understood in terms of this opposition? The problem of spam, for instance, doesn't really feel like a privacy deficit. Efforts to opt out of information networks aren't necessarily motivated by privacy.
Instead, the spirit of unconnection is fuelled by the Miesian aesthetic, 'less is more'. Unliking, unfriending, unconnecting will one day emerge as acts of social brutalism, analogous to architectural brutalism. They won't seek to alienate or criticise anyone, simply to minimise and cleanse. We have the phenomenon of undesign in web design, which I assume shares a similar aesthetic principle. The problem is that we're not talking about objects, buildings or pixels on this occasion, we're talking about people. It's all very well being a modernist when it comes to non-human actors, but what about where non-non-human ones are concerned? At some point we'll need it to be OK to say "it's not that I dislike you, it's just that I unlike you..."