Blizzard Entertainment has started to send emails to provide a barcode to all those who purchased a Blizzcon 2009 ticket. I confirmed with Nethaera these PNMI.com emails are legitimate. That company specializes in Secure Online Registration Systems for trade shows, conferences and associations. They seem to be contracted to handle the barcode registration for Blizzcon tickets. You should double-check your Junk Mail in case this email is sent there. Beware of any emails asking you to visit a URL link and asking you to login and enter your password. These are fake.
Simply Print out your barcode, and keep it safe with you to turn in at the Anaheim Convention Center booths. If you were among the fans who won a ticket through any of the fansites contests, you must bring this barcode to the VIP booth which is usually located on the far right of the entrance.
Blizzard will release an official statement in the next few hours. Stay tuned for updates.