3: to normalize anonymity so that people in groups 1 and 2 stand out less, have less peer pressure to compromise themselves, and so that attackers have to spend more resources than if they could focus their attacks on the few people they actually want to target (compare HTTPS Everywhere and other "Encrypt all the things!" efforts).
> [2:] to isolate yourself from online mobs
If we're talking about common, I'll add:
3: to normalize anonymity so that people in groups 1 and 2 stand out less, have less peer pressure to compromise themselves, and so that attackers have to spend more resources than if they could focus their attacks on the few people they actually want to target (compare HTTPS Everywhere and other "Encrypt all the things!" efforts).