This reminds me of the time where Blizzard wanted to do something similar for their forums as people would troll often. From what I remember, there was a huge backlash. They seem to be trying to take a safer approach by suggesting you do it versus forcing you. I wonder if they had that incident in the back of their mind when taking this approach.
This is a little bit different because it's only giving users with pre-existing accounts an option to change their username to their real name. Anybody who registers a new account is forced to use their real name (or a fake real name).
For those interested: http://www.escapistmagazine.com/news/view/101916-Blizzard-Fo...