I will start off by saying that I occasionally tether, but only when I am somewhere that I do not have internet access for my laptop. At these times, I limit what I access, some work files, long email responses, etc. No streaming of video or audio on my laptop while tethered. I un-tether until an event, like a work email I receive on my Droid, indicates, I need to access the internet.
Unlimited is a misnomer in the real world. There is a hard mathematical limit on the bandwidth that cannot be exceeded in a day, week, month, whatever time limit you choose.
Does the old 80-20 rule come into play here? That is - are 80% of the resources (bandwidth) are used by 20% of the people?
I have been on the unlimited data plan for over 5 years. Over the past 5+ years, on Treo, Droid, and Droid 3, I have exceeded 5 gb exactly 1 time which basically was double my 2nd highest usage. Normally, I am right around 1.5 gb. I could be a lot higher, but I make a conscientious effort to use WiFi when possible.
I feel I have a right to unfettered access to the relatively small amount, compared to many, of fast bandwidth when I use it. If Verizon needs to throttle back folks that are using, in their estimation, an exorbitant amount of bandwidth, I FULL SUPPORT it.
Even when throttled back, you still have 'unlimited' internet access; it is just at a lower speed.
Remember, the language of the TOS is based on the internet usage on the phone, not on unlimited usage of the network.
Just my $2.00 worth, my thoughts are worth 100 times more than the old 2 cents.
These are my opinions, most likely, your will differ.
Bob