Sure we can't compare this exclusive network with App.net but believe me, Twitter having gazillions of people does not add any value to me. It makes my day harder, because every day more shit is produced in Twitter and Twitter is focusing on # of people vs # of advertisement clicks. They don't care about me. This is the old T.V model and I don't have a cable at home any more.
I'm entrepreneur and a programmer. If App.Net brings in VCs, marketers, entrepreneurs and good programmers I'm in. I will pay $10-$20 p/m to be in that network. App.net will care about what their users think. They have to.
It's not about the # of people, it's about the value they create; the content they write, the links they share, the conversations they have.
I don't care if 2M 16 year old Justin Bieber fans joining to the network. No value to me.
http://www.kk.org/thetechnium/archives/2008/03/1000_true_fan...
If you think about how Twitter needs to reach 100 of millions if not billions of users to possibly become sustainable, or figure out how to squeeze more money out of the users they have. Then compare that to the App.net proposal. Especially the part about making the user the customer. Then you can see how having a small set of faithful users might be more sustainable.
Dalton wrote more about this in his post: http://daltoncaldwell.com/an-audacious-proposal
disclaimer: I work for App.net, but this post represents my own views.