I personally keep one or two ships untagged for good reason these days. Take this example that happened previously.
>Log on official tagged ship 1 in System B, move to system A
>Exactly two minutes later, Officall tagged ship 2 logs on in System C
>Half a minute later, Faction 2 ship enters System A
>After a minute, Faction 2 ship finds faction 1 ship
>Faction 2 ship engages Faction 1 ship with superior weaponry(in this example, a Gunboat v Light Fighter).
>Two hours later, on Faction 2 Bounty Forums, Faction 2 ship demands the bounty payment for the Faction 1 ship, as well as the bonus for the ship being officially tagged. Faction 2 ship profits while Faction 1 ship has to deal with ruined RP and more frustration in the game.
>Next time Faction 1 ship enters game, it has to hide well above/below(200k at one point) to dissuade Faction 2 from coming into System A again for more easy money.
The faction tag is more of a target sign for people like bounty hunters(and general trolls(im looking at you too)) so it should be allowable to keep it off, else no one would join an official faction.