I have two Honda 2000i with the parallel kit. I take both when we know we will need to run the A/C or other high draw appliance. I only take one if no A/C is needed.
The edison company was doing some work in the neighborhood and damaged a transformer so the power went out. They came around and said it would take up to 48 hours to get a new transformer in place. So I brought out the two Hondas and we were the only house on the block with power for the 36 hours it took to get commercial power back.
When boondocking, I chain the generators to the frame of the trailer using a heavy logging chain and a one inch cable lock used for motorcycles. I use a heavy lock like this on the logging chain: http://www.masterlock.com/business-use/product/220KA
So far, knock on wood, no theft.