I think this is very short sided of Tesla. They have created an incredible Owner Community. Getting Owners to do their selling. People want to thank others that help them learn and want to buy a Tesla. The amount of the referral can be changed as the Company evaluates the demand, but they should allow buyers to thank owners. You can come up with relatively cost effective Thank You's Doesn't have to be unlimited supercharging for life or $1000 or a free Roadster if you get a bunch of people.
You should always be able to enter a referral code and even give an owner a credit.