The big networks filter such traffic, the small networks benefit from it.
https://www.reddit.com/r/legal/comments/1pq6kgp/is_it_legal_...
You may also get accidentally get your own website blacklisted or moved to a lower RPM tier, or provoke shadow-ban websites that you like to visit, or... generate more ad revenue for them.
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.