The reason we see them try to pull this BS (and frequently get away with it) is because customers let themselves get pushed around, walked all over, and generally taken advantage of.
Its not so much a matter of letting one's self being pushed around. Its more a matter of there being no alternative. Look at where TWC was trying out caps: nowhere near the areas where they have real competition from Verison's FiOS. That leaves areas that the best competition is DSL where if you're close enough to the CO maybe you can get 3/768. Interestingly, TWC's announced cap trial (and public backlash) in upstate New York prompted Frontier (the LEC in some areas) to abandon its own plans to cap their DSL service. This does seem to be an outcome of lack of decent competition in most areas.
They don't want to scare off new customers by advertising any limits, but at the same time they want to enforce limits. Can't have it both ways.
Oh, but they want to. They've seen the dollar signs in their eyes and right now are regrouping and working on how to re-introduce caps after better "educating" the customer on the urgent need for their implementation. Look at the price structure for the caps (and overage charges): its all about raising the price of users who they think use ("always on") service too much while being able to say that the ISP didn't raise their prices, and I would go so far as to use the term gouge in some cases.
Take AT&T's 3G mobile Internet service which they sell for $60/month. The plan limit is quoted in GB (5 GB to be exact) but the overage amount is quoted in KB. A person who doesn't know any better probably doesn't know what a KB is verses a GB and that 1 KB is 1/1,048,576 a GB. The price sheet is purposely misleading.
At 0.00048/KB for overage, that's 503.32/GB. Either AT&T is selling the first 5GB at a huge loss or their overage charges are unconscionable
Imagine going to a restaurant on a saturday all you can eat buffet to have a big breakfast with your family, and as you are parking you see the advert in the window for saturday morning all-you-can-eat, and notice the little note at the bottom, "(we will kick you out if you eat more than $20 worth of food)". Tell me YOU wouldn't find somewhere else to eat breakfast? So it's not surprising they don't want to disclose anything like that.
For Comcast (prior to last year) and now it seems TWC, its more along the lines of, "we will kick you out if you eat more than we think you deserve to eat" but without telling you what that threshold is or that there even is one. When you consider that the limiting factor is not the bandwidth from the ISP to the internet or the cost of it there. It is from the head end to the user where you have very oversold nodes; in the case of TWC, they're been fairly resistant to upgrading to DOCSIS 3 which, while a band-aid, should provide more available system bandwidth. And yes, a lot of it has to do with protecting their video revenues.