Dropcam wasn’t innovative because it was a webcam. There were probably hundreds of webcams on the market when it launched. What made all the difference with it was the ease to set it up and to access and record video with it.
Before that, you had to connect webcams to a PC and configure recording or streaming software. You might have needed an RJ45 cable to a router, or maybe even a brick-like power adapter.
For awhile, we had a Dropcam in the office. After awhile, it seemed to fade to the background. I know longer paid much attention to an always listening and watching video camera (though did turn face it away at times).
While a camera can seem invasive because of the potential creep factor, microphones seem to be more acceptable. What probably decreases the sensitivity is that 1) it’s not likely that the microphone is streaming audio and storing somewhere and 2) it has an immediate usefulness to the person it’s recording. Those two items are critical for us lowering our guard against devices.
If those conditions are met, we’ll be more comfortable with mics hiding in plain sight — opening up the door to truly ubiquitous voice experiences.