There's no avoiding it. If you play World of Warcraft, you're going to need a Battle.net account, as Blizzard has set a drop dead date for the great account switchover. Don't worry, it won't hurt a bit.
You just better have it done by November 11, as Blizzard will be requiring it for WoW players, not to mention future games, like StarCraft II and Diablo III. Better yet, it's easy, free and will net World of Warcraft players a virtual penguin to pal around with in-game. There's even a FAQ!!
Hit up the official site for a brief explanation of why Blizzard considers this switchover a good thing.