Apparently many people were confused at the startup screen of StarCraft II, and may of entered in the wrong name to represent themselves in online play. Blizzard understands this, and apologies for the confusion. They're also offering a free name change for everyone to give players the second chance they deserve at obtaining the name they want.
This one-time offer will also be followed up by an additional feature, the ability to pay in order to change any name more than once. It's a neat feature, but one that will really only serve more harm than good in the long run. Odds are more players will change their name to hide from a bad reputation more often than they'll feel the urge to just change a name for fun.
Slightly hilarious in the face of the recent Real ID drama. At least everyone who's made a mistake naming themselves gets a second chance.