Nerfing heavy users is the cheapest maintenance option while keeping the profit high.

8/10 friends of mine who uses streamyx just download anything everyday/ night which usually comes up to 8GB per week. 10GB as OP stated isnt alot per month and i have reached 14GB last month due to downloading a new purchased game digitally, have yet to receive any letter from TM.

Still stay safe and dont be greedy, use the bandwidth wisely and you will get to get away from the throttle. Dont think that you must use to the limit with what you have paid for.