I've nearly always played anon on my toons, I played a ranger back on AB before I quit and became somewhat obsessed with making plats and killing oldworld mobs. The problem was other people did the same thing - being anon lowered the competition. If I know all the other people that are farming as soon as server comes up I can move through zones to targets much much faster.
Another reason I went anon (while guilded, I was in raiding guilds my whole 3-4ish years on AB) was because I simply wanted to do something without being bothered or being found. For example - raiding with friends in a different guild (doing content far below what we were currently farming so the lockouts didn't matter), or one grouping raid instances for augs or alts or something. Used to get told off all the time for that, apparently some people are under the delusion that being in a guild requires you to display your tag the entire time. 'Course the guild window on live shows your location when you're using /role and it makes your name purple & that bugged me
[You must be logged in to view images. Log in or Register.] so /anon it was!
People shouldn't use any argument that has to do with "you shouldn't be hiding from your guild mates". Sure, I'm guilded with them, but that doesn't require some sort of mystical bond that lets them know where I am and what i'm doing every second i'm logged in. Shit, I don't even have to like the majority of them in order to be guilded with them. If I've just finished a days work and want to chill out and buff people in crushbone rather than doing some long boring camp to twink a guildies alt that they can't solo, that's my choice. Anon helps avoid situations like that.