Same problem in Newfoundland, Canada
I have the same problem with my 2012 Ford Focus. Got the car Dec. 7/2011 and had to bring it back on Dec. 9/2011 with the same fuel gauge issue. They replaced the vacuum purge valve and it seemed to work for 2 days, then it went again. I filled the tank up completely then 1 hour later it showed a notch above empty. And I only drove the car 5km. Going back to the dealer again today and I hope they can fix it or they may be getting this car back.