Gmail Warns Of Suspicious Account Activity
Although the new feature isn't remarkably accurate (in the US it only displays which state you are in), it can prove useful if an attack comes from across the country or from overseas. Since there are plenty of legitimate reasons for accessing an account from multiple locations, Google doesn't lock you out of the account. Instead, it simply displays a warning message and provides an easy way to change your password.
The message also provides detailed information so you can see the latest account activity with information about the most recent access points. If the access was legitimate, you can click "Dismiss" to remove the message.
Recognizing security is also a high priority for businesses and schools, Google plans to offer this feature for Google Apps in the future after it has gathered and incorporated feedback.