It's a hoot to imagine, but Matt Baldwin's musings on Flash Mops is also kinda telling about how online communities really don't 'spontaneously organize' in any practical social sense like Matt proffers:

Here's the plan. Everybody meet up at the house at 1765 Parker st. N. (98101) on that Sunday morning. Then, at exactly 10:00 AM we'll completely clean the place

This is where the first 'second superpower', the fragmental networks of loosely joined environmental and political action anti-globalization orgs, have the edge and more rights to the title: It's painless to pop a quid or two into a candidate's PayPal or to relay a few bits to expose some hypocracy or promote some notion from a comfortable chair, and it's undoubtably a hoot to go meet a hoard of singles in a Holiday Inn bar and bounce like bunnies for 7.3 minutes or hassle a carpet clerk, but it's quite another level of social power to amass with strangers in the face of shielded riot police and take in some fresh tear-gas and pepper-spray on a bright summer's morn ... or even to swarm Matt's kitchen like a white tornado.
And why not? Why shouldn't scrubbing the tiles at Matt's house have just as much opportunity for mass perplexity, social stimulation and plain old-fashioned opportunities to get laid? Power is work done over distance, so if there was any 'spontaneous organization' going on, why should the social impetus anneal to Theatre of the Absurd instead of Random Acts of Kindness?

Have there been any instances of Flash Mobs doing positive action? Smart Mobs swarming for the Greater Good?

I'll not be surprised if there have been charitable swarms where the kindness escaped the Google net, slipped below the Blogdex remarkableness radar ... or even just slipped through my aggregator unnoticed and uncited with narry an echo to underline it. Still, if there have been FlashMob RAOK events, the news must have been fleeting, and they've not been heard above the din of the dino worshippers.

Still, I'd like to believe there are Angel FlashMobs, great synchronized hoards anonymously swarming in to hack a playground from some trash-strewn parking lot or leaving no chore undone at some worthy senior's home.