I hear this refrain most often from non-technical people. My response is always that it's a waste of resources and unnecessary to listen to your conversations.

I hear this refrain most often from non-technical people. My response is always that it's a waste of resources and unnecessary to listen to your conversations. Advertising companies can infer what you talk about with other people based on proximity to each other and subsequent actions like visiting a website. If two people stand next to each other and talk about going to Las Vegas, and one person looks at flights to Last Vegas later on, you could probably show ads for flights to Las Vegas the person they were standing next to and have them click on it.