Web APIs without Registration

Dharmesh Shah has a list of attributes that make a great web API. I've not actually used the Digg API, but I've used others enough to sound a hearty Amen. Point #4 is my favorite, There's no registration and no key that has to be requested. Aside from making the API harder to use, registration processes discourage hobbyists from experimenting. It unnecessarily truncates the long tail that makes web services so valuable. Registration and API keys are a remnant of walled garden mentality. I prefer the lazy, trusting approach. Allow everyone to use the API assuming that they'll be good citizens. What if scoundrels cause trouble? Cross that bridge if you get there. No sense penalizing yourself and honest users because somehow, somewhere, someone might abuse your API.