With today's announcement by Twitter CEO Dick Costolo of the Tweetdeck acquisition, the shape of the next layer of micro messaging begins to come into focus. What BetaWorks CEO and co-founder John Borthwick was calling hypothetical yesterday when we talked backstage at TechCrunch Disrupt is now a fait accompli, if it wasn't already so then. He described how Betaworks was at work modeling a desktop multi-column Twitter UI when Tweetdeck founder Ian Dodsworth popped up with a working app to invest in. But when I tapped on my iPad, Borthwick called it the device that changed everything.