According to an Amazon employee, Alexa devices sometimes captures users having sex, and its recordings are sometimes heard by staff members.
It's no surprise since Alexa devices (and Google, Apple, etc.) can sometimes catch random things around the house, like arguments, fights, private discussions, kids teaching Alexa how to say bad words, etc. According to a whistleblower at Amazon, 0.2% of accidental Alexa recordings are manually analyzed by team members based in Bucharest, Romania, Boston, Costa Rica, and India.
Source: The Sun