The barcode system is a new one for Blizzard. You will need to print out the email you receive and bring the barcode with you when you pick up your badge at the convention hall. We highly recommend picking up your badge the day before (Thursday) so you can enjoy waiting in long lines to get into the place on Friday morning for the opening ceremony.
You should receive a separate email and separate barcode for each person for whom you bought a ticket for. My tickets are going to a few WoW.com staff members, and the first of them came through this morning. Another email came this afternoon.
Initially we were not going to run this story until we heard from Blizzard directly that these emails were real and legit, however a very large number of people are reporting receiving their barcodes. The barcode email comes from pnmi.com, which is not a blizzard.com address.
Because of this we have contacted and are waiting for Blizzard to verify the email. We'll update this post when we hear back from them. I find it perplexing that Blizzard would drum into our heads for years telling us only to trust a blizzard.com source, and then have a massive email sent out that isn't from blizzard.com without telling us about its legitimacy before hand.
Update: Blizzard has confirmed these emails are legit.
So check your email and check your spam folders! My guess is that sending out all the badges will take a day or so.