at 64k, you can do about 20Gig a month if you abused it. at 128k - 40Gig a month.
now given generally 1Gig costs about $1 to an ISP, you can see why they dont offer anything over and above 64k, in fact at 64k, they can still incur alot of costs..
Lets examine for a moment the wording. "Your data cap" . Now really, this means youve reached a limit. You have paid for some data, and now youve exhausted that supply. Why would ISP's ( who actually are trying to make money you know ) give away ANY data after your cap? What would happen if they acted like a cell phone company? You reach a limit you MUST top up. I dont see voda giving away a reduced amount of txts per hour just cause you hit your pre-paid amount.
Throttled plans were introduced by ISP's to protect themselves and uneducated users from spyware/malware infections/errant p2p usage on mom and pops computer. Spyware/malware can typically lead to some massive suprise bills at the end of the month especially when hijacked for p2p.
It was bad PR for the ISP's to charge Grandma the huge bill and it was bad business to let a user unintentionally use that much data
I can't really see why anyone would want to be throttled unless you're on a very tight budget where you can't ever spend more than x per month on internet. Like I said before I think it's a waste of time and effort for the ISP to optimize their service for a minority in this case.
There is certainly value in having throttle on cap plans for your general consumer audience. Price certainty can often be quite important, even if it does mean being throttled - hence why flatrate dial up was so popular... pay one price, access the internet as often as you liked.
Sure, more technically minded people will find throttling inhumane, but there are options for them. Telecom for instance offer their Business broadband plans, Slingshot offer datacaps, and WorldxChange gives you the option to avoid being throttled completely.