If you have good invalidating prior art, re-exam is cost effective and scary for the patentee. Not only can it knock out the patent, even a small change to the

If you have good invalidating prior art, re-exam is cost effective and scary for the patentee. Not only can it knock out the patent, even a small change to the claim language in light of the prior art during re-exam means that the patentee can not collect damages prior to the modification. This affects the troll's current target and past and future licensees as well. Even if you don't go into a reexam, it is a stick to wave to try to bring about a more reasonable settlement.