> Because the substrates are open, users can relatively easily switch between centralized services, How is it easier for me to switch from Facebook to somethin

> Because the substrates are open, users can relatively easily switch between centralized services, How is it easier for me to switch from Facebook to something else, if it's carried over the Internet as opposed to something proprietary like their own modem pools for example? I can't think of a single service for which that is true. Facebook is the lock in, just as Microsoft is the lock in for office PCs even if the underlying technology is somewhat open.