Yahoo's search APIs

Yahoo's APIs are easier to use, and more featureful than Google's. You don't need SOAP to access the services. You can search web pages, images, and news articles at Yahoo (Google only lets you search web pages). Both services rate-limit queries made using their search APIs, but do it differently. With Google, you apply for a developer account, and get an id that you send with every query. If you hit your limit, your developer account can no longer make any queries until the end of the day (actually, 24 hours from the time of the first query). Yahoo asks you to apply for application ids instead of a single developer id. You're asked to get a separate application id for each application you write that uses their APIs. This lets Yahoo rate-limit each application separately. In addition to that, Yahoo's rate-limiting works on an IP address basis -- if you were to distribute your application to a bunch of users, they'd be monitored and rate-limited separately. Compare that with Google's case -- once your developer id hits the limit, nobody can query Google with your application for the rest of the 24 hour period.