http://groups.google.com/group/twitter-development-talk/browse_thread/thread/8ac4c0a09c171a52
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1. There will now be "sender" and "recipient" elements that contain
the standard user attributes inline with every direct message. This
saves you an API request if you need to know more about the sender or
recipient of a message than just her ID or screen name. The existing
sender_id, recipient_id, sender_screen_name, and
recipient_screen_name attributes will be deprecated next month.
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