Hi there, just a quick note to say that at My Opera (http://my.opera.com) we developed and sent live an integration with Twitter that allows our users to see their friends timeline in their latest activities "stream" on My Opera.
The number of active users is not so high, and we cache twitter API calls for 5 minutes currently, so it shouldn't be a big problem for Twitter :) For now we are using basic auth, but the OAuth integration is ready and will completely replace the basic auth version in our next release. Thanks Twitter team, -- Cosimo