On August 25th Techcrunch noticed that Twitter appeared to be tracking outbound clicks on their web interface, but that the redirects seemed to disappear after the downtime afterwards.
It looks like the links are back, I was just using Twitter.com and noticed the outbound links, which are of the format:
plus an authenticity token. Looks like they’re tracking the link, where it’s come from, what tweet it’s come from, and the userId of the user that clicked it (in this case me).
It’ll be interesting to see if this sticks around, and I bet it’s part of the analytics service they might be providing to paying customers. I’m not sure how it will stand up to bit.ly analytics (which of course, they blessed) especially as bit.ly analytics will work on any service, not just the web-based interface. They could also use this to muscle in on Tweetmeme, and they could track links by clicks rather than retweets and extend their trending topics system to include trending links, though how accurate this would be at determining popularity when it would largely depend on the number of followers (clicking takes a lot less effort than retweeting) is questionable.