Single links drastically change the network
mpg.de
mpg.de
A new connection is more likely to come from someone with a large number of connections (since they will be making larger numbers of new connections than someone who is unconnected). Therefore, a new friend will have more friends than you and, in relation to this link, will bring a lot more to your network.
[1] http://www.guardian.co.uk/lifeandstyle/2010/jan/30/change-yo...