j1m+5n0w's Journal: Wikipedia link of the day: Network Effect

Network Effect:

The network effect causes a good or service to have a value to a potential customer dependent on the number of customers already owning that good or using that service. Ergo, it means that the total value of a good or service that possesses a network effect is roughly proportional to the square of the number of customers already owning that good or using that service.

One consequence of a network effect is that the purchase of a good by one individual indirectly benefits others who own the good - for example by purchasing a telephone a person makes other telephones more useful. This type of side-effect in a transaction is known as an externality in economics, and externalities arising from network effects are known as network externalities.