What the government is saying by allowing these rights to be sold, is that the place to which they are transferred to has arbitrarily restrictive zoning. In my mind, the value of transferrable development rights should be zero. Zoning should actually have some hard principle behind it that isn't bendable by allowing the non-development of some other desirable piece of land. Either a building is too tall for the neighborhood or it isn't. It should be "too tall unless you pay a farmer 10 miles away".
Why is uneven, concentrated development some kind of public good?
How does this position unroll? How does the farm eventually get developed in 50 years? Do they have to buy TDR from someone else? Does an "equivalent" TDR have to be demolished?