I have o2 unlimited web, it came free with my upgrade. I will be using it with the n900 when it arrives. On the bill it says my allowance is 2GB I have once gone over this and nothing happened. I have heard if you have persistently high usage they may have a go at you, but I haven't heard of anybody that this has happened to. Frankly I struggle to go over the limit in the month, and I do use it for youtube etc what stops me going over is when I am near free wifi e.g. at home I use wifi.