After I searched for ATL in Google Maps it told me that ATL was the airport name for the Atlanta Airport, it's like it's Google Suggest but only of places you searched in the past.. (see image)

http://i4.tinypic.com/24crvgg.jpg

Is this new?

That's being generated from your saved locations.

That came out in the past week.

AH! I thought that might be what that was, I didn't know it saved the locations automatically.

You can change that setting under the "Saved Locations" link in the top right. By default it saves locations automatically, but you can disable that as well as add you own (with custom labels).