I used to think this, until I happened across FullStory. With that tool you can replay a website visitor's exact session as if it was recorded live on video -- everything they typed (even if it was cleared and never sent in a request), where/when clicks happened, the contents and response of every request, etc.

As a backend engineer, I had no idea that frontend monitoring was this advanced, but apparently it is. So now we all have to be extra paranoid, because _any_ website could be using this tool to "spy" on everybody.

Of course, it _was_ very helpful to us in tracking down some issues (ever tried to tell a customer how to send you a HAR?). And I assume that operating with an adblocker and blocking nonessential cookies will prevent or hamper the output for us more technical types. Even so...