Tim O’Reilly writes persuasively about the virtues of allowing people to follow you without you being required to follow them back. He calls this “asymmetric follow” or “Twitter-mode”. This ability is one of the key advantages that Twitter has over other networks like Facebook and Dopplr which require you to response to friend requests in order to grow the network.
With Twitter’s model, I can find people I’m interested in, whether or not they know me, and learn about them and their lives and thoughts. Others can include me in their lists. You become “friends” with complete strangers over time, by communicating with them (responding with @messages for example), perhaps by mutual following. In fact, Twitter’s wonderful system of @ messages means that anyone can address me – and so I find myself having conversations with complete strangers as well. I actually follow my @ messages more faithfully than I do my planned Follow list.
His advice to all social networks: “even if you have your own ideas about how to organize social networks, have an option for users to turn on ‘Twitter-mode’. I think you’d be surprised how well it works.”