...if you use a LOT of data (I define that as over 5 GB, others will debate that) it may very well put you on their radar screen and they CAN (a) terminate your service, or (b) charge you out the butt per MB, or (c) BOTH. They can tell what's phone data and what's tethered data... and while I have yet to hear of Verizon actually doing it, somebody is going to be the first and they will be made an example of. Most of us tether lightly, as necessary, and encourage restraint. It will only take one person tethering torrents or something to ruin a great thing for everybody.