They could actually exploit it as a business feature. Make the flic.kr domain point to Twitter's servers, who implement the shortening service, and allow the business users to view lots of interesting stats, in relation with tweets. Stuff the business on its own could never gather without access to Twitter's extensive database of tweets.
This way both win. Twitter could charge for it as well.
That's... one of the best Twitter monetization ideas I've heard.
It pushes Twitter's real-time social analytics value to businesses while obviously strengthening a company's brand on Twitter. If the Tweet Button catches on, it could be a very easy sell.
This way both win. Twitter could charge for it as well.