I recently read about this issue. In fact, it may have been in Straight Dope, I can’t remember. But people here aren’t the only ones wondering about being spied on by Google. Turns out that spying on people is so 20th century. Google and many of the major tech companies, Facebook for one, uses artificial intelligence to model the behavior of every individual. You already have a doppelhanger at Google. The AI monitors a few general characteristics about your current behavior and predicts specific future events about you. They don’t actually listen in to your conversations, but as an example they know that when a person just like you calls their sister, that means you are likely to do something similar to what your sister is doing. If you sister is surfing the web looking at shoes, the AI will start serving you shoe ads. etc. They didn’t listen in to your call, but they know who you called etc.
All very spooky and so far ahead of the law that legal issues simply aren’t a factor. They aren’t monitoring your activities, they are monitoring an AI creation of you that they created. That AI creation doesn’t have any privacy to violate.