To clarify, I'm not affiliated with App.net in any way (aside from being a backer). Just an idea I had that I thought would be cool, and make App.net really useful to me as a user and developer.
One question: What happens when a piece of middleware fails respond, becomes overloaded, goes out of business, etc?
I think the App.net client should just show a little warning saying "{{middleware_name}} no longer responds. [Disable] [Retry]"
I think it's possible that the above comment about the middleware had to do with the fact that afaik, most middleware implementations are chained so if one fails then the next is never called.
Out of curiousness..what support will App.net have for analytics/data? Obviously this is a more user driven platform so I'm curious what data will be supported or what the intent for this API would be besides publishing.