Question for all the car guys/gals...

I am not a car idiot, but wouldn't call myself savvy. So, here is the situation I would like some feedback on. My wife got to her car this afternoon after work only to realize that she left her keys in the car...in the ignition...with the car still running. That's right folks...my teacher wife who educates our future leaders/brain surgeons/cigar smokers left her car running for 9 hours. Now my question is, can this cause any real damage other than about 10 gallons of wasted gas?

She has a 98 Acura RL with 24,000 miles on it. The car is in great shape but is obviously a few years old.

thank you in advance for your comments regarding the car and also mocking the Mrs...