Tilter;233441 wroteIf you do jailbreak your iPhone, there are apps to use for tethering such that you will use data off your plan, and won't be charged for data by using it like a modem.
I personally have a Teksavvy DSL Plan ($27.99/mo for ulmtd bandwidth, uses Bell Services) and have a Rogers Lite Cable Modem as my backup.
I don't pay for tethering, just use data off my plan.