Their bottom line.

My guess is it's an effort to dissuade customers from piracy.

Most ISP's (in the US anyway) are also big media companies. Time Warner and Comcast are 2 examples of this. They hate p2p because they believe it takes away from their sales of movies and tv shows, as well as advertisement on the networks they own through lower ratings. It's likely that other smaller ISP's are in collusion with the big media conglomerates. (I have no idea if Rogers is also a cable/media company like Time Warner and Comcast.)

Supposedly p2p networks also can slow down entire internet speeds, which I guess can be true but I'm not up on the technical aspects of bandwidth so I can't give a more exact explanation of how that works.

I don't know how internet is served in the states, but here in the UK most ISPs do it because they have to.

Most internet in the UK comes through the telephone line, and whilst we pay for speeds of "up to 20mbps" for example, most customers will only get this outside of peak times. If there is heavy local usage then the speed available to each customer may only be 10mbps as the total bandwidth at the telephone exchange is shared between all customers. Now if customers all decide to cap their speeds downloading the latest glee episodes or twilight movies then the available bandwidth at the exchange is reduced and so others have a poorer service. By capping speeds either at peak times or for certain protocols ISPs are able to provide a service that can be used by all.

Personally I think it sucks, but I understand it has to happen. I'm just willing to pay a little bit more to get the best service in my area. I don't know how my 40mbps connection (with no shaping, throttling or anything else - I always get 37mbps+) compares globally.

@Pyromelter

As i am one of your northen neighbours, I can say yes that Rogers Canada is our equivalent to Comcast, Time/Warner in the US.

Although I don't have their Internet service but am on their smartphone plan, it sucks balls and I hope they fix it.

Their argument isn't so much based on piracy (although media can grasp that and it's a popular button) as it is on general bandwidth.

All connections are not equal. Many companies take a 100 mbps uplink and sell 5 mbps connections to 50 people. They get away with that because, in general, nobody uses all 5mbps constantly so they can make the claim if it's the truth for four or five nines of availability.

With the advent of p2p, netflix, etc., it is possible that more than 20 people can actually hit all 5mbps at once. So the ISP solution is QoS. What connections to people NEED to have going full throttle and what can we conveniently claim is normal network lag and still claim the connection is as fast as ever? Well, a netflix stream affects visual quality, a game affects playability, but p2p just kinda goes until its done, so it's the one to get shafted.

Now it's also mighty convenient, and most likely is certainly one of the considerations, that the media has spun p2p as being nothing but piracy, so a complaint of p2p speeds might as well be an admission of guilt to most. Still there are reasons of logistics and not just legality.

I know of at least 2 reasons they don't like p2p stuff.

1) It costs them money for every byte going to other ISPs/networks. There are interconnect fees between these networks they negotiate, so it costs a couple pennies to transfer data.

2) (more likely) The ISPs lie to you when they sell you X mbps Internet. They run a high bandwidth hub to an area, and people share this hubs bandwidth knowing that not everyone accesses the Internet at the same time. That way they can sell like 250mbps+ on a 100mbps connection hub. If multiple people start downloading and hogging this pipe, your neighbors don't get as much of that window and they complain. Then it costs them more to put a bigger pipe to you.

http://en.wikipedia.org/wiki/Rogers_Wireless