Onavo, an Israeli start-up, just announced it was being acquired by Facebook. Onavo’s flagship product is a data compressor. When you browse a Web page or use an app on your phone, Onavo routes the traffic through its servers, where it compresses and optimizes the data before sending it on to the phone. Call it “small data.” The result is you see exactly the same Web page but less data comes out of your plan. This makes a big difference in markets where users are loath to exceed data limits for fear of punitive charges.