One of my favorite sayings is that I love when good things happen and I don't have to be involved. I don't think its original with me, its an expression that anyone who manages anything has thought at one time or another.
Web services are like that. In this article on Loosely Coupled, Phil Wainewright talks about the Bookwatch Plus service and what makes it all possible: namely services offered by five different companies, people or groups who didn't know beforehand that their service would be used to create this book watch service.
Tim Oreilly writes: "Innovation will come from APIs that support 'unintended consequences'." Bookwatch Plus is perfect example of Tim's point and what we're trying to promote with principles like those in my Enabling Web Services article.
I used to teach programming language design and theory. One of the great lessons of programming languages is that if you put a feature in, some clever programmer will figure out something cool to do with it. The same is true of creating good services, making data available in ways that enable future use, and documenting the resulting APIs so that others can use them. Cool things will happen.