https://www.cnbc.com/2019/04/11/how-to-stop-amazon-from-listening-to-what-you-say-to-alexa.html

On Wednesday, a report from Bloomberg revealed that thousands of Amazon employees are listening to what people say when they talk to Alexa.

Amazon said it uses these conversations to improve Alexa's "understanding of human speech." Bloomberg's report said that the voice snippets are tied to device serial numbers and the owner's first name.