I actually ran down a Cadillac CTS in the pit lane at Gingerman two weeks ago that had his gas tank left open. At least he didn't get out there, unlike this person. There really should be someone checking cars on the pit lanes before they are allowed on track, but not all organizations have that. I think all the BMWCCA schools I've ran with have that (not trying to put down Trackdaze, I've ran with them once, and they run a good school). This may happen more than you think, since it seems the tendency is for drivers to remember to fill up right before their session, and track gas pumps are usually a bit odd, and drivers get in a hurry and forget the routine.
2011 Jerez Black/Fox Red E90 M3 DCT, ZCP, ZCV, ZCW, ZP2, BMW Apps
2004 VW R32 (track car)