I have been following the Adhearsion project for some time, under the advice of a colleague - and its tech guru Jay Phillips has crafted a masterful essay on the limitations and technological glass ceiling Asterisk it currently has. It is a must read.
I concur 110% with all of Jay's conclusions, and having worked with several IP/PBX vendors and start ups over the past few years, the underlying theme of my suggestions have been as follows. MAKE it easy, and I mean drop dead simple - to develop an ecosystem of applications.
Time and time again - I am met with the same answer - Yes, we have to do that - and then they never do.
Hopefully Adhearsion makes it a reality.