If the function of patents is to incentive capital markets to invest in products and processes that otherwise wouldn't see any investment because of the lack of a profit motive, then patent trolls are a good thing. The whole point of a patent is to grant a monopoly. Whether a patent holder enforcing the monopoly is a non-practicing entity (NPE) is immaterial.
Indeed, by the logic of the patent system so-called trolls are an unmitigated positive. They add liquidity to the patent system. Liquidity means the patent system, theoretically, is more efficient at incentivizing research and design.
If you have a problem with patent trolls, then it means you have a problem with something _else_ fundamental to the patent system. Maybe if you followed your beliefs to their logical end, you would question the validity of the necessity of patents. Alternatively, maybe what so-called patent trolls are exposing is the fact that patents are too freely granted, or granted for too long. Or that being able to sell patents at all, whether to NPEs or other companies, is just an end-run around anti-trust laws, which would otherwise blunt how rigidly a company could leverage patent rights in a market.
In any event, there's nothing negative about patent trolls, per se. They're simply exposing fundamental flaws in the patent system. I fear that focusing on so-called patent trolls will simply result in superficial legislative and judicial solutions.