"Comcast still has subscribers? Why?"
Because we have no choice. In terms of faster-than-dialup Internet access, we have between one and five choices, depending on whether each of these is available in the area:
1. Cable -- Provides access to the entire town/city. You are limited to the one cable company providing service to your area. Moderate price.
2. DSL -- Provides access only to customers within range of the CO, does not provide access to to entire town/city. In reality, you are limited to the one phone company, though you may be paying someone else who effectively leases the line from the phone company. Low to high price depending on maximum speed and type of DSL (ADSL, SDSL, etc).
3. Satellite -- Provides access only to areas which can get a clear signal to/from the satellite. Some services require dial-up for upstream. Typically there's zero or one providers available. Expensive.
4. Cellular -- Provides access only to areas which can get a clear cellular signal. This is the option which has the most competition because while there are only three of four companies to pick from, "three or four" is still more than the "one" available with cable or DSL. Extremely expensive.
5. Fiber -- Provides access only to specific areas of specific metropolitan cities (at least in the US). You are limited to the one phone company. Price unknown.
My friend just bought a house, and DSL isn't available, so his only choice is cable. My only choices are cable (Comast) and DSL (Verizon). It's easy to say "you should leave and let your money talk"; it's another matter when you have no other option. That's why we call them monopolies.
re: "Have separate subscriptions" @ranga
I couldn't agree more. In fact, I'm sick of subsidizing all those wimps who feel the need to use SSL when paying by credit card. Don't they know SSL takes up a lot more bandwidth? I'm also sick of subsidizing all those people who endlessly forward email and those who use HTML email. Don't they know all those forwards and all that HTML content uses a lot more traffic than plaintext? Don't even get me started on base64-encoded attachments...
In case you couldn't tell, we call that "sarcasm". An ISP shouldn't care what protocols a customer is using. What they CAN care about is how much traffic and how much bandwidth a customer is using (you did know that traffic and bandwidth aren't the same thing, right?). However, since Comcast sells their service as "unlimited", they have absolutely zero right to complain about any traffic or bandwidth issues arising out of a customer's use of the service.
But since you feel so strongly about it, may I ask why you feel that P2P is worse than any other protocol (for instance, HTTP)? If my neighbor wrote a book and distributed a text copy of that book via P2P, how is that any worse than me VPNing into a client and transferring backup files? Or somebody using Google or another space-for-rent host and uploading files to the host for backup purposes? Hint: it's no different.
The only legitimate thing any ISP can do is throttle an individual user for going over a specific threshold (whether that threshold is traffic, bandwidth, number of connections, etc). And even that is not legitimate when the ISP sells their service as "unlimited". In no event is it valid or legitimate to throttle a protocol. What's next? Throttling HTTP or HTTPS once enough BTers start using ports 80 or 443? How about throttling HTTP (80) and SMTP (25 and 587) for everybody if one customer is sending out lots of spam? Maybe throttling DNS (53) if people still insist on using names instead of IP addresses? You see how stupid it sounds? But in reality, those scenarios are no different than what Comcast is already doing. And if you even think of saying "But they would never do that!", please bang your head on your keyboard until you're unconscious.