[AnthonyMouse]

> For the idea that patent trolls add liquidity to the invention marketplace, I'm under the impression that the cost of acquiring the patent in question is often only a minor component of the operation, and the major cost is litigating it. Which seems to suggest that the primary economic effect is something else (what that is I'm not sure).

The phrase you are looking for is administrative overhead. Which suggests that obtaining "liquidity" via patent trolling is highly inefficient and should be discouraged, because the bulk of the money is going to overhead and not incentive for innovation.