Adam Bosworth's most excellent blog has a mighty interesting snippet
I'm trying, right now to figure out if there is any real justification for the WS-* standards and even SOAP in the face of the complexity when XML over HTTP works so well. Reliable messaging would be such a justification, but it isn't there. Eventing might be such a justification, but it isn't there either and both specs are tied up in others in a sort of spec spaghetti. So, I'm kind of a skeptic of the value apart from the toolkits. They do deliver some value, (get a WSDL, instant code to talk to service), but what I'm really thinking about is whether there can't be a much simpler kindler way to do this.
I'm not sure if I should jump in with my obligatory flurry of links to mod-pubsub and other 'notifications over the Web' technologies, since I'm pretty sure he knows about them.