Twitter is currently riding on venture capital funding. Their only revenue stream is the advertising they run in Japan (and only Japan). Twitter operates at a loss. As far as I know, they plan to open up to revenue opportunities soon, but that it is not a priority. They don’t seem very interested in ad money. In my opinion, Twitter has a lot of opportunities in terms of additional services they could offer to businesses. The thousands of business customers that actively use the service could well do with having analytics available to them; such as how their followers are finding them, profile views to follower conversion, and more. If they did choose to go down the advertising road, it might make more sense to be able to pay to have your business’ Twitter account featured as an ad, rather than traditional banner or text advertising. It’ll be interesting to see how they finally choose to make money.