They said it will be like battletag names where you can pick any display name you like in game (so yes... there can be a hundred Zeus) but the game assigns an identifier to the name so that your friends can still see which one you are.

In battletags its just your name is BOB#1245. Only the Bob part shows in game but when you want to friend someone you have to add the number too. Dunno how exactly similar or different this will be. In battle tags the number I think it is randomly generated so its not like the first person to create it gets BOB#0001.

That way there is now way for players to enter the game on day1 and stock up on awesome names to sell later :3