If you are currently using BT as your ISP and you have the misfortune of using a BT Home Hub 2.0 do be aware that this device has a potential security flaw allowing BT to update/change firmware settings on it without your consent.

This gives BT the potential to track your internet usage from inside your own network, even seeing the network that passes inside of your own LAN.

If you have implicit trust in BT as a highly ethical company that never does anything wrong (infringing GPL, RIPA breaches) then you should carry on using you're Home Hub, if not.. be afraid...

source http://community.bt.com/t5/BB-in-Home/Why-have-BT-put-a-backdoor-in-the-8-1-H-J-firmware-that-allows/td-p/620