> a proprietary centralized system that can block or cut them off for any reason.

As a startup founder – chatlio.com – betting on the Slack "platform" I have to say that it feels pretty great to know that they are not planning on cutting us off tomorrow morning... :) Might happen anyway of course, but this announcement means we can work somewhat more serenely for a while longer. I see this as a kind of "stability pledge" to third party dev shops.