A proposal (in “Radical Markets”) I agree with is to charge a property tax of, say, 2% for each year that a patent holder wants to keep the patent. The value of the patent is whatever the owner decides it should be but (to prevent claims of $1 values) the owner must sell the patent to the first entity willing to pay more than the declared value.
This, in theory, would ensure that only patents that were genuinely useful would be kept around rather than being used as tools to stifle innovation or rent seek for those that actually create great works.
