Username or EmailPassword
Why this BT obsession? They have enought money to pay servers. Maybe they're getting hammered now but that's probably because they want it out soon - not because they don't have the resources to put enought horsepower to make it fly.
BT is wonderful when you don't have enought resources to buy docens of servers, but this is Microsoft. If you have money just go with HTTP/FTP servers - they're better: P2P implies you must upload data, FTP does not. If I'm paying money to a company to provide me support I don't want to waste bandwith just to help them to download things, I pay money to have less problems, no more.