Remember when console.log was available when the dev tools were open but would be undefined otherwise, so your code would break unexpectedly but then work fine when you tried to figure out what went wrong?
Back in the day I used LiveConnect[1] for this and other purposes[2]. I would dump errors to an IRC server so that I could collect the results. I could also respond with code that would be eval'd making development very easy.
Not sure there was much risk: The web application used a private IRC server with name+password registered users. L3 support who /msg'd a user session some JavaScript doesn't seem likely as the messages were all logged, and anyone with fileserver access could just put whatever they want in the <script> tag anyway...
Remember when console.log broke ie? Debugging was fun.