It's not that hard to settle out of court and the threat of selling your patent to a patent troll enables you to leverage the threat just as well as the big guys. As to defending yourself, if you don't have the resources to mount a reasonable defense your not worth the cost of a lawsuit.
It's 2nd hand, but I do know someone that uses vary narrow patents to make a decent secondary income stream. Granted, this probably does not work as well for broad software patents, but make the cost benefit analysis obvious enough and you don't need much in the way of sticks.
