Mac App Store updating problem
You can log out from the App Store after you click "Account" at the Quick Links sidebar (inside the "Feature" Tap)
  You can log out and change the Apple ID inside the OS X settings
  You need to log in with the Apple ID you bought the apps with
  You can delete certain apps and keep the files. Like iPhoto keeps its Library inside the Pictures folder in your Home directory 
  You have to buy the Apps again if they cost money if you want to update them with your other Apple ID