It’s Uber for buses, sort of: A new start-up called Bridj is setting up a “pop-up” bus service in Boston. Thanks to data gleaned from sites like Foursquare and Facebook, the company will send buses along routes where its customers are most likely to be. And Bridj ought to have plenty of customers; Uber will likely be the first of many success stories in the growing field of app-based transportation services.This is travel in the 21st century, folks. At the moment, Bridj is more expensive than Boston’s bus and rail system. But at $6 (as opposed to the T’s $1.50–2 fee), Bridj’s fare might appeal to many a commuter looking to escape crowded, slow, and often unreliable public transport.As is common these days, however, increased efficiency goes hand in hand with a loss of privacy. We expect this trend to continue; the new economy is both a service and an information economy, and big data is likely to give rise to more new and unexpected services like Bridj.