Happy to announce two new API methods today, delivered in response to developer demand for an easier way to keep tabs on users' social graphs. The methods, /friends/ids and /followers/ids, return the entire list of numeric user IDs for a user's set of followed and following users, respectively. Responses to these methods are cached until the user's social graph changes. The responses come direct from our denormalized list data stores, and should be reasonably fast even for users with a large number of followers/follows.
These new methods are most useful for services that are maintaining a cache of user details. If you see a user ID that you don't have cached, you'll have to call /users/show to retrieve that user's details. But for services with large user bases, or those that simply want to diff a user's social graph over time, we hope these methods will come in handy.
You can find the documentation at http://apiwiki.twitter.com/REST-API-Documentation#SocialGraphMethods.
-- Alex Payne - API Lead, Twitter, Inc. http://twitter.com/al3x
