The other thing I would say about this is that it seems like some (liberal secularists) use, or try to use, the web for this kind of thing -- writing 'moving and energizing sermons', networking with like-minded folks, recommitting themselves emotionally to their causes, developing plans for proseletyzing others, conferring on strategy. (And to a much lesser extent contributing money, although it tends to be to particular candidates rather than to a centralized organization. I don't know how singing songs applies on the web.) Of course this isn't restricted to progressives.

I think this will probably become more common, although I would hesistate to predict how effective or significant it will ever be in the larger political or social scene.

A lot of the stuff that gets written is distorted or kind of dumb, but I think that that is probably inevitable for this sort of thing (regardless of whether it is online or not).