Wouldn't those apps just be App.net clients? If you're limited only to what types of media App.net provides, how can you make an innovative app?
(Note: app.net might pull those dirty tricks in the future, but at least they've got a business model that doesn't _require_ them too)
In short, App.net is something with the potential to build a business on, whereas anyone trying to build a serious business (as opposed to just doing something cool) on Twitter is an outright fool at this point.
what on earth makes you think they are not?
I understand the vision. But I also understand, as someone who has used app.net, in actual fact, simply porting your social graph into a new app does you no good. You still have to convince all your friends to also get that same app before they can see what you post with it. The vision only works with basic media, like text, and photos, posted in a very straightforward twitter-like way.
I'll give you a specific example: Group chat with photos. Yep, there's an app.net app that does that, and now, you can't see the photos unless you have that app. so what's the point? what's in the vision for this situation?
My basic point is, the app.net vision is fundamentally flawed. It's not just a matter of positioning/marketing. It's the same fundamental flaw that google wave had. The vision is that app.net is a protocol, but you can't market protocols to people. you can only market apps. or more specifically, you can only market specific solutions to specific problems, or some fundamentally human vision (rather than a technological one)
With the app.net vision, any app you get that happens to use app.net as a back end will be subtly and frustratingly broken in some way because there's this feature, or that feature that your friend used that you can't see, because you have the wrong app. There's no commonality, there's no ultimate app that does all the things. With twitter, at least you get a link, something everyone understands, to a webpage, read in the ultimate universal client-a web browser. On app.net you just get mysterious silence. and "oh, that didn't work for you? huh..."
app.net is the linux of social media. Nerds love it but mortals will never get on board.