Replying to @null and @therevoltingx, @BrendanEich, @samtingleff, @acfou, @kickstand, @mrr619, @WolfieChristl, @johnwilander, @johnnyryan, @brave, @random_walker
Of course the party is key. Talking to someone directly and talking to someone while another person hides outside the room listening through the door have completely different characteristics and must be treated accordingly.
It's possible to get consent for profiling, but it has to render the implications clear for any profiling variable that may be detrimental to the user. Facebook has a pretty bad track record there.