The Activity Streams format has already been adopted by BBC, Gnip, Google Buzz Gowalla, IBM, MySpace, Opera, Socialcast, Superfeedr, TypePad, Windows Live, YIID, and many others.
Out of those, Google Buzz and Gowalla no longer exist, and Windows Live and YIID have changed names.
The front page reads:
Out of those, Google Buzz and Gowalla no longer exist, and Windows Live and YIID have changed names.