I have just started reading The Laws Of Disruption by Larry Downes, which already has the feeling of being a cracker, and in the opening chapter he discusses, amongst others, Metcalfe's Law. For those of you unfamiliar with this law it can be paraphrased as "the usefulness of a network is the square of the number of users connected to it"
This as why from the word go numbers matter. You can't afford to be choosy about who joins your networks or why - you just need bodies. In corporate settings don't get arsey about who should or shouldn't be using your social media tools or what they should or shouldn't use them for. You can't afford to care. You need numbers and you need them fast. Do ANYTHING it takes to get them or you will end up with a dead system on your hands.