From Blizzard Entertainment:
We wanted to let everyone know that in the near future we’ll be allowing everyone a chance to change their chosen StarCraft II character name for free.
In some cases, people chose character names that don’t represent their usual multiplayer nicknames, as they were unaware of how the character names were being used. It’s important to us that everyone is represented by a name of their choosing in their multiplayer games, ladders, and on the forums and community site.
In addition, beyond this initial free name change, we’ll be launching a service similar to the one we offer for World of Warcraft which will allow additional character name changes for a fee. We'll announce more details on how the free name change and additional paid character name changes will be implemented in the near future.