Companies providing this networking service must realize then that the only thing they have to fear regarding losing users is their own stupidity. With this in mind, if they were to open up an API to allow other social networking sites to hook into their massive database, then they could offer interoperability as a selling point. These networks do not compete on technical merit, only on size of their audience, as that has a direct effect on more people signing up with their service. True, if they offered interoperability, someone might shop around for a place to host their profile, but then again, most of these people are the same ones who would sign up because their friend gave them a link to the service they were given a link to and so on and so fourth.
This open API would provide unending advantanges for the consumer, and a good number of positives for the service provider. The only ones losing out are the people who enjoy having to cross post across three to seven million different services and people like that probably also like watching paint dry. I have no sympathy for those folks.