But, given that many of the larger ISPs (at least those available to residential customers in my area -- Comcast and Verizon) are owned by companies that also provide cable (and telephone) services, what's to stop them from simply bundling cable service with your internet service and charging a bunch extra? I realize that not everyone has this problem, but in many areas there's almost an "information monopoly" with regards to web service.

That is a problem, I'd agree. In my case at least, those companies provide the option to buy internet without having to buy the other crap.

Also, here's a moble MVNO which does a lot of things right:

https://ting.com/

Now if only you could easily bring your existing phone onto their service...

p.s.

I should have said, "delivered over internet protocol such that I could get the service through my choice of internet provider". Decouplable, in other words.