If Path or App.net can show verifiable success in their respective ventures it will likely lead to other services copy-catting the idea of charging their users for the service they are offering. I can certainly think of worse things to copy.
While I can’t bring myself to trust Path (what is this of Dave Morin using a day and night phone?), I can certainly get behind this notion of copying paid services.
I think the key to offering a paid service is to be paid from day one. Path is going the opposite route and that never seems to work in the long run.
If people know they need to pay from day one then the standard has been set. If the service then offers free later on (with reduced whatever) that service stands a much better chance of converting free users to paid users because the service has never been devalued by being free in the consumer mind.