As previous posters have said, not uncommon. I have an 07 JKU and had it happen to me. Depending on the build date of your 07, dealer may or may not replace the tank. Funny thing, the tank model number on the 07 is the same as 08 and 09, so why they won't do it for all 07's is beyond me.
What I found with mine is that it did it in colder weather...but not in the Summer, etc. Dealer said cooler tempatures cause the change in pressure that closes the flap thus causing the spill over. Now...I call B.S....however, it happened just like he said. Another thing to do if the dealer will not swap out your tank is to fill up, and as soon as you hear a little gurgling...back off the nozzle. Don't go full bore with the gas nozzle. I read that in another forum and that worked pretty well, too. Reduced the amount of gas spewing everywhere.
Good luck getting your tank replaced!!