Automatic sign in and missing data
Because your Google Apps account now works more like a full Google Account, your browser's cookies will be carried across products at sign in. That means that if you visit another Google product while signed in to your Google Apps account, you'll automatically be signed in with your Google Apps account.
When you’re automatically signed in with your Google Apps account, you will see only data associated with that account. If you previously used a product with another account and are then automatically signed with your Google Apps account, you either won’t see data from your previous account or you might be asked to set up a new profile for that product. Don’t worry—your data is safe. To access this data, sign in with your previous account.
If you'd like to be able to access multiple accounts at once in the same browser, you can enable multiple sign-in. If you do not want to enable multiple sign-in, you can still access multiple accounts at once, just not in the same browser.