traffic shaping

Or in other words, as your Internet provider, prevents you from sending files via BitTorrent at your top speed.

Google did a study and published the world results here:
http://netneutralitymap.org/

If they choose to BitTorrent in the upper left corner, then click on "you Country" on the map, a list of operators that make TS EN appears.
Incidentally, can test your connection here http://www.measurementlab.net/tools/glasnost and contribute to the accuracy of the study of Google