Frustration with ATT business practices will not be solved by customer 
complaints. Let's look at the network physics.

(At least as I understand it) "Cable" TV is really cable access TV 
(CATV). Coax cable has a serious signal loss, limiting signal integrity 
to small areas. Thus, many separate local area networks are assembled and 
really just downloading a satellite signal to your host TV or computer. 
Each download site is, in effect, a hub (bridge). The CATV network is not 
much different from a large, fast ethernet network. 

The advancement for the consumer is that now coax enters your home (or 
office) instead of a phone line. The bandwidth linking you to the rest of 
the world has made a big jump.

ATT held a monopoly on telephone lines, and that was ordered broken up. 
Now they want a monopoly on your coax line. Old habits die hard.

There is no physical reason why other internet access providers can't 
share the coax. And there is ample legal precedent that they should.