I believe jaems33 is referring to the phone being used as a hotspot. I can, almost literally, watch the battery drain when I put my wife's Android phone in hotspot mode.

Also, there are more popular 4G data plans now, such as T-Mobile's "No Annual Contract Mobile Broadband Passes" that you can enable on-demand, only requiring once-year usage to keep the account active. I'm not sure if other carriers offer similar plans.