Battle.net has a system set up for their 'Battletag', which is the username you display when playing any of Blizzard's games. Your tag can only be so long (which is why mine is cut down to 'PredictedCy' right now), and has a 4-digit code slapped to the end which you either need to memorise or look up every time you're you're trying to tell people what your tag is.
Up until recently, you could only change that tag once after making it. It was free to do, but after that change that was it - that was your lot. You could never change it again so if you ended up disliking the change, you were stuck with it. Now however it seems there's been a quiet little update and you can change your Battletag as often as you'd like - provided you're willing to pay for it.
The first change is still free, but every change after that needs the new Battletag Name Change which is now available as a Battle.net Game Service for the price of $10. You're allowed to buy and change your tag as often as you want to, so if you're the sort to change your mind on your online tag often, you're now able to keep your Battletag up to date like your other accounts.
Blizzard don't seem to have announced this change anywhere, but people have been asking for it for a while so I don't see anyone complaining about it.
