Its Blizzard , they brought in some elements of World of Warcraft into it - the RealID system that allows easily to invite people into party and keep track of their progress - The always on acts as anti-cheat system , to prevent people from hacking and selling things in auction house and making money. This is to prevent memory editors , something like how VAC works when you connect to VAC System. If you can't authenticate to VAC Server , you are kicked out.