I started networking on-line about 3 years ago and soon learnt a simple rule:

"Build the network before you need it"

Not everyone wants to do this. Some people only want to network with people they know and trust. That's fine.

But I wanted to reach out and discover new people with new ideas. So I joined may on-line communities/networks and just started making contact with people. In the last 18 months from those few thousand initial contacts I have built many very strong relationships that have been good for social and business from those contacts.

Don't pester people. Be genuine and open. One day you will find a reason for working with some of those early contacts - especially if you don't force it. Building a network is like any construction project or gardening - build solid foundations, plant many seeds, care for the results and you will be well rewarded.