If you're traveling and expect to use Maps to navigate, Google to scope out enjoyable things to do, your email app to keep in touch, Instagram to brag, Foursquare to keep tabs, Facebook to kill time and your cloud drive of choice to sift through flight and hotel confirmation PDFs, it'll be dangerously easy to exceed 100MB in a day.
ENGADGET: iPhoneTrip SIM rental review: the best way to keep your smartphone connected while abroad