On Phil Windley's Enterprise Computing Weblog he has a positing talking about Walled Gardens vs. Networked Effects
. This neatly summarises the problems relating to trying to limit your customers on a network to the services that you have direct control over (wall garden); telecommunications services are usually seen as being in the category. This is contrasted with open networks where it is easy for anyone to offer services over the network; the Internet and the Web are usually seen as being like this. He concludes that many broadband networks are actually inbetween, where it is easy to consume services, but not easy to create them yourself.