Breaking fog can be very annoying, but it is legal. If you do break the fog you might expect retaliation from other players as well as the owner of the position you gave away. It's likely that someone else can read the log and knows a bonus has been taken, so often there's not much point. However, if your playing a big game where no one can see anything, e.g an 8player Classic in the early rounds or something and someone takes an early bonus you can inform the other players of it and spread misinfomation about your own position with a statement like, "wow- the log shows, blue is growing fast and unchallenged? Did he take Ireland? I can't see the top!" You may well be at the top, but why not let someone else break him?
Finch