[eftpotrm]

But a company on the scale of Microsoft have the resources to systematically dismantle their patents, track down prior art, produce material demonstrating that the patent in question is demonstrably 'obvious to anyone skilled in the art' and so on.

Lodsys's product range is their patents which they license and / or sue on. They lose by their patents being demonstrated as the worthless nonsense they truly should be, at which point they're gone completely - it's a bigger loss than having to pay a license for a product or rewrite a component.