It doesn't matter a whit whether VZW can or cannot prove that you are tethering your Droid. If they determine from the amount of data traffic to/from your phone that you probably are tethering they can simply slap you with an additional $30 per month charge which is the difference between your "unlimited" data plan and a "broadband" plan.
The latter IS limited to 5 gigabytes per month. So they can simply charge you additional per megabyte charges above that limit if they like.
If that happens it is up to the customer to either "prove" they are not tethering the Droid or pay the additional charges. If you refuse to pay the additional charges they can terminate your service for non-payment.
Where do you get your information? The way you're describing it, if I rack up a lot of traffic I'll get pegged as a tetherer, even if I'm using the device as intended, say to view hi quality movies. Can that be right?
The way some people are describing it, VZ informs customers that they KNOW tethering is taking place. I think they might just be analyzing the data of heavy bandwidth users. I'm just speculating, but these things make me think that tethering software that encrypts and proxies may be the future.
If you "rack up a lot of traffic" Verizon can decide you are you have violated the terms of your ToS and charge you for the overage. Period. If you don't like it, you can (a) not pay your bill and/or (b) take legal action.
If you're prepared to (a) ruin your credit and/or (b) test your attorney's skills against the army of attorneys VZW has retained, go for it.
If you read your service agreement you'll see that it was written to provide Verizon with presumptive power to prevent "abuse" of
their network with the phone they have
purchased for you. You don't own your phone free and clear until your service agreement is over and Verizon is perfectly free to decide how their network will be used and to determine if you have used it in the way they license.
I realize that few people understand the nature of the contract they sign when they commit themselves to a two year "lease to buy" a phone, but virtually all contract law places the burden of proof on the customer and the power to redefine or terminate the contract on the part of Verizon.
That's why the entire issue of whether VZW "knows" that tethering is taking place is irrelevant. They don't have to prove anything.
P.S. Where my information comes from is having been married to an attorney and having taught constitutional law.