Network monitoring firm Arieso is attracting attention this morning with a new study indicating owners of Apple’s iPhone 4S consume twice as much data as users carrying the previous generation iPhone 4. But what’s less clear is why, exactly. Bloomberg claims Siri is to blame, while Ars Technica says any such claims should be taken with a grain of salt. But CNNMoney’s Philip Elmer-DeWitt rightly puts things into perspective by noting how much is being consumed by users attaching their laptops to cell networks with a dongle. That makes sense because nothing eats up as much bandwidth in mobile as video — and larger devices like laptops and tablets are much more video-friendly than even the biggest smartphone.