Starting today Twitter will begin experimenting with commerce. It’s the latest effort to expand the atomic unit of a tweet beyond 140 characters. The implementation is straightforward: a big “Buy” button that will appear alongside an image of the item for sale. Give Twitter your billing and shipping info once and you can make one-click purchases from inside a tweet if you’re logged into the app or web service. The big question on Wall Street’s mind is whether this might provide the company a meaningful secondary stream of revenue alongside advertising. The more interesting question for the average consumer is if the real-time nature of Twitter might produce some interesting new forms of business we haven’t seen yet.