Google recently made available a very useful feature called Multi Account Sign-in to its users, though this feature is very useful, currently it is limited to only 3 Google Accounts.
If you try to sign in to more than 3 accounts with the Google Multi Account Sign-in Feature enabled, you will see an error message similar to the one in the image above. The error message says:
You are already signed in to the maximum number of accounts. If you want to use another account you must sign out of all Google Accounts then sign in to the account you want.
So, currently to make use of different accounts, you will first have to sign out of one or all of the Google Accounts you are currently signed in into and then sign-in to the account you want to check. Though this is a minor constraint, it would definitely be good if Google would allow users to access around 5-7 accounts at once.
I know many users who have around 5 accounts minimum for various purposes. In addition to that, it would also be good if Google allowed users to sign-in with Google Apps accounts too.