I wish social sites forced me (and others) to apply some level of selectivity in creating my network.
Lots of cell providers are offering plans where the customer gets unlimited calls/chats - but only to a prescribed set of friends/family members. As the size of this social network is constrained (and there is a cost to the customer), the customers will choose its members carefully. Also, knowing that they were selected/invited with care, its members would (might) appreciate the honour.
Would that the same effect applied in social sites, where there is almost no cost for sending an invite. To the sender that is, the cost (of reading the email, trying to remember a relationship, logging in, accepting the invite, etc) is borne by the invitee. I bet few people get invites from un (or barely) known strangers to join such a 'calling circle'.
I predict that, eventually, providers will offer tiered discounts to 'friends of a friend'. For instance, I'd get free calls to my 1st tier 5 friends, 50% off for the 25 members of the 2nd tier, etc. I expect I'll have to pay full rate to call Kevin Bacon.