The other day Piers Harding asked me why XMPP publish-subscribe technologies haven't taken off yet. Since Piers was at the 2002 meeting in Munich where we had some lengthy discussions about pubsub, he knows that pubsub has long been a contentious issue (e.g., it took us a long time to make peace between those who wanted to do event notifications only and those who wanted to persist items for later retrieval).
Here are some possible reasons:
I suppose we were ahead of our time by working on pubsub back in 2001 and 2002. But that's not uncommon. As I like to put it, we build the runway and we make it as long and smooth as we can; what kind of aircraft you build and where you fly the plane are up to you. :)
Peter Saint-Andre > Journal