My favorite is the anti-drug ad that states "30% of wreckless drivers test positive for marijuana" giving the impression that those who test positived are stoned.
Officer to stoned driver: "...and who do you think is going to pay for the damage if you drive like that, young man?"
Stoned driver: "Not to worry officer, I'm a wreckless driver."
"It's amazing what you can learn from DNA." - Desdamona.