The reason I'm going with duct tape is that the black electrical tape I have is so old that it doesn't stick to anything anymore. And yes, I'm too cheap to buy some more!

Imabenz - does your car have the clear plastic film on the body where the hatch bumpers make contact? Mine are starting to break apart and I've had to reglue them down a couple of times already. Looks like I'll also have to find another way to protect the paint in the near future.