I worry that widespread camera tracking is an effective route to determining identities of otherwise anonymous online accounts. If you can work out times when people are unlikely to be posting content online (e.g. because they are seen carrying bags of shopping) you can gradually, through process of elimination, work out who is the real identity behind some online account, or at least some probability. For example, if I make some number of posts on hacker news, every person who has an 'alibi' at the time of a post cannot be a candidate for the true identity of the account.