I'm with you... and I'm glad you mentioned it. I suppose it's only fair to add a disclaimer that illegal tethering CAN and WILL be found by your carrier (eventually all carriers will have ways to tell) and you WILL be in violation of your contract and can therefore be subject to "who knows what" that is in the fine-print...
NOT a good idea to do it.
I've tethered using USB and PDANet (before root) a handful of times. Of course I didn't have a 4G phone so my speeds were a neck-breaking 1.x-2.x MBPS lol... Only really used it in a pinch and in all fairness I really didn't know it was a large violation of contract, just kinda figured it was a "tisk tisk". My average data useage since I've had a smartphone (a little over a year now) is still under 2GB per month.