You deliberate harm and financial damage using a computer bot. Almost all countries have provisions where you can be sued for any type of damage you cause and be asked to repair it (a minima at the civil level).

Big ones detect it, so they don't care to sue. Small ones benefit, so they don't sue.

This is your main protection, there is nothing to squeeze from a single guy. Even if you get him to pay you back the fraud, then what ? It costs more in legal fees.

Still, it's such an odd concept to self-inflict yourself such; it's way better to just block the ads than to be tagged as a bot and get Recaptcha-ed or Turnstiled more frequently.