Phil Windley has a very good writeup of the session on Mashups, Web Data, and APIs from the WWW2006 event. Panelists included Dan Theurer from Yahoo! on their APIs, Kevin Lawver from AOL, Frank Mantek from Google on GData, and Jeff Barr from Amazon.
Interesting points from Jeff Barr on API provider best practices:
- First, have a program: Plan your API, don't just throw it out there.
- Get the business model right: Have a strategy, plan for licensing and pricing.
- Get the technology side right: Support multiple formats like XML, JSON, and REST. Remember versioning (something that a large percentage of APIs here do not)
- Support developers: Including samples and documentation
- Create community: From forums to blogs and outreach
He's also got a bit more on the conference here on his ZDNet blog.