[holowoodman]

You may either rent/buy a device from your ISP, or you may bring your own, at your discretion. ISPs are required to accept all devices, of course if your device kills the network segment, they will kill your connectivity. But they can't refuse to let you connect.

[direwolf20]

What happens if your device connects 1000 volts to the cable and fries everyone else's device and the head-end?

[holowoodman]

You get taken to court and sentenced to pay the damages? Same thing that happens with the TV cable that runs through the whole street. Or the cars parked openly along the road. If you damage it, you pay for it.