CO2 tank in or out of kegerator?

I'm modifying my fridge and I still have not decided if I should drilled an extra hole on the back for the gas line or if I should just leave the gas tank inside. what are the advantages and disadvantages of having the gas tank in or out?
If humidity is high inside, would corrosion of the gas tank be something to worry about, since it doesn't have any paint on?

The humidity could play a small roll positioning of the tank but more importantly you should consider the space it takes. If you tank is nice and shiny then it is probably aluminum and shouldn't corrode too easily.

If you can fit the number of kegs you want and the tank then put it inside, if not, drill a hole. I currently keep mine inside but I plan on adding a few more taps and kegs so I will be placing it on the outside of the fridge soon.