My connection (30Mbps down, 1Mbps up) used to have a limit of 40Gbytes/month (mixed up and down).
Fortunately they had "Happy Hours", from 1 to 9 (AM) traffic wasn't counted, which was great, since theoretically - with 30Mbps - you could use ~3Tb in one month, I know I always used around 200-300Gbytes/month.
Then came the "unlimited" and sooner or later people found out that "unlimited" meant 250Gbytes/month, you exceed that and they will:
- Send you a registered letter that tells you to stop using so much traffic or they "might" cut your connection if they think you're abusing.
- Phone you once in a while, saying the same as the letter.
Now, I personally would have nothing against it, if they defined what is an "abusive" amount of traffic. The problem is that they don't define it, refuse to define it and yet expect people to follow the rules. People only know the "unlimited" is 250Gbytes/month because lots of people (mostly P2P users) started receiving the letters/calls when they hit the 250Gbytes.
I understand unlimited is impossible, I even think that every ISP should have a traffic limit, that way at least people would know what to expect. But then I'm against any limit under 500 Gbytes for connections over 10Mbps. That and up speed should be at least 1/10th of the down speed, eg. 30 down/1 up is simply ridiculous.