People get these confused and I think it is a good distinction to make.
The differences between social networks and on line communities are listed below.
Social Network
A social network is a social structure made
of nodes (which are generally individuals or
organizations) that are tied by one or more specific
types of interdependency, such as values, visions
ideas, financial exchange, friendship or trade.
http://en.wikipedia.org/wiki/Social_network
Large and distributed with many nodes (Facebook, LinkedIn, etc.)
Social ties = weak
If you are NOT there, you probably ARE NOT missed
Online community
A virtual community, e-community or online community ..
