Originally Posted by George Knighton

You can pretend you're somebody on the same block. That'd be the easiest thing to do. If you and your neighbour are box taxing the service beyond whatever the nominal cap is, however, you might draw attention to someone's having bootlegged a modem. Most cable caps are so high right now that it'd be pretty hard to raise an alarm.

Or you could fairly easily rotate evident IP addresses within unassigned numbers on the same IP so that nobody could find you. A lot of people do this for security...my own evident IP is not my real one, for example.