That's also true for baby cams. Worse than that, a lot are actually sending the video over the internet and watching it "locally" actually goes through the cloud.
I believe pacala was talking about regular mics in cars and baby systems that are not connected to internet (I have products like that).
Of course there are different products that are constantly connected to the Internet, we hear a lot about them on HN's front page.
Except, of course, that they are.
For example, OnStar has been around for ~20 years and there are documented cases of FBI using it to eavesdrop on their suspects.