Whenever I see several different groups behaving in a manner I find obnoxious, I wonder incentives encourage this kind of behavior, and how those incentives might be reduced.

One such way is countersuit, which Rackspace is doing. If everyone (successfully) countersued, the incentive to be a patent troll would diminish.

There might be other ways. Is there some common property patent trolls depend on that might be penalized or forbidden? I've noticed that patent trolls rarely seem to produce anything. Perhaps some sort of "use it or lose it" clause, in which patent holders have a certain amount of time to effectively license their technology to some degree of effectiveness before they can't enforce infringements.

It works in other areas. For instance, in my home state, many people would love to live in the country extremely cheaply, so there's an incentive to set up dubious Christmas tree farms to get nice tax rates. To combat this, you have a certain number of years to turn a profit, and if you don't, you lose the farm credit.

(here's an example of why they do this: http://www.huntingnet.com/forum/wildlife-management-food-plo...)