It is not worth getting yourself all worked up and angry over some inconsiderate jackazz who is violating your property boundaries. Unless that person is actively causing damage or creating a dangerous situation, they should be dealt with as you would any other minor offensive behavior.
Furthermore, if you lay a booby trap and it injures someone, you could potentially lose those boundaries you are so fond of.
Its just not worth it.
Taking this a step further, it's one thing to take that action,(Board with nails) and accept the liability yourself... IMO advising someone else to do so is just a bad idea.