Anthropologists have found that for one person, a genuine social network – one in which you know the members and they know you is limited to about 150 people. In fact, Malcolm Gladwell, author of The Tipping Point found there is a "'cognitive limit to the number of individuals with whom any one person can maintain stable relationships."
So what does all of this mean to you: DON'T NETWORK JUST TO NETWORK! Whittle down your contacts to the most fruitful ones. Then rank them according to their importance until you've created 1st, 2nd, & 3rd tier networks.