I am not sure how I feel about these session recorders and probably want to start blocking them from my browser. It is akin to someone recording your every movement inside your house and watching the video to see what issues come up. Oh and you have no idea its happening.
Also wonder about how this data is protected. If videos of how I used Facebook were leaked (messages I started to type but didnt send for instance) it would be a huge violation of my privacy.
In the same token, its like free UX research, you can see where people struggle by watching them use the app. It is like standing over someone's shoulder to see how they are using the product and helps immensely in that realm. I still feel like it should be opt in though.