Even worse, if you've got multiple Google accounts, you can't use them at the same time. So if you've got a separate junk email throwaway account, you can't be logged into there and Adwords or Docs at the same time. You can skirt this a little bit with Google Apps and have an email + other Google services open, but kind of a pain in the neck, especially if you manage a couple different businesses/projects/whatever that should have their own email addresses.
