And while I'm at it, Joe's latest entry is about Enterprise Mashups.
I wrote about this in January in the context of why software standardization is so important.
But unlike this thread of blog entries starting with Joe's latest, I view enterprise mashups as a combination of publicly available and proprietary services. Unlike purely Web-based mashups, enterprise mashups are going to include services visible only inside the firewall. Companies are just not going to share services that represent their competitive differentiation.