1. Awesome invention, straws that detect adulterants and change colour 2. Obviously people do get drugged occasionally, the inventor seems to have had it happen to him 3. Unfortunately there seems to be no real evidence that GHB or ketamine are often used in sexual assaults, and even Rohypnol which has the worst reputation has not often been detected. A straw that could detect a drink that's stronger than you think i…
Uncommon is pretty broad, if something as severe as being drugged happens to one person out of every 200 each night, it is "common" in my mind.