The problem with 12V batteries - its all about probability.
Older style lead acid batteries (which 99% cars use), the plates would actually become fragile and brittle if not kept charged, and that caused the battery to fail and the battery dies. The newer style are gel style, which is what Tesla uses now. They cost more (like 50 bucks more), but they last longer. Lower probability of failure, but still they can fail. The problem is, Tesla being energy efficient does not supply enough current to keep the 12V happy. If you drive a lot, its not an issue. But if you drive < 5K a year (like me), then you have a higher chance of the 12V crapping out. This would be the same if you had an automatic and to save on gas if you pull your car in neutral on every downhill. Some cars keep the alternator engaged (german cars, toyotas) even in neutral, but some cars (like Hondas/Acuras/Infinitis) disengage the alternator when in neutral. You do this neutral hypermiling for a month, you'll need a new battery.
So while I agree with Hank that the camera draws very little current, don't underestimate the power consumption of a draw that is on ALL THE TIME. It does increase the probability of battery failure, albeit by how much - its hard to guess. Batteries are random luck to begin with. But yes if you left the camera running in an airport parking lot in the dead of winter for 2 weeks, it does increase your risk significantly .. I feel so .. and its what I will make my risk assesment on.
That said, you could buy a jumpstarter lithium ion battery pack for 40 bucks on amazon. It can give you a jumpstart in a pinch, and doubles up as a flashlight. And even out of warranty, Tesla 12V battery replacement will be 4-500$ (battery itself is $130-$150, plus maybe 1-2 hours of labor, Tesla decided to bury the 12V battery in a deep orifice of the Model S .. Why Fremonters .. WHY!?).
Lets just say, the 12V battery in Tesla isn't the best engineering.
There are three things every self respecting Tesla owner must have in their trunk,
1. That jumpstart battery
2. Jumpstart cables
3. The Tesla tire repair kit (50 bucks, but also can be used to keep your tires at the right pressure, use it every month).
I am making a very nice list of "what to purchase after getting your Tesla"