Was wondering if an official SL one was ever implemented. If not I wouldn't mind the burden of starting one. A Bingo Book in general is a good way to let someone know a little about another person, ICly. Without all that ooc knowledge thrown on the computer screen. It would be very basic and reveal nothing personal, just standard name, height, weight, age, affiliation and if there are any bounties on your head. Other information can be included, specific to said individual. The bingo book is meant to be up to date, thus if someone was to attempt an invasion in lets say Konoha for whatever reason and they succeed small scale and flee, later on such news would be attached to their bingo record in a note of their involvement. Further more if Konoha wishes to have the attackers dead, a bounty can be set up for imaginary loot of course, in which people can bounty hunt for said nin; given information from the bingo book. This could allow for real bounties to be set in place as well, along side the use of a bingo book. Basically allow you to decipher if a nin is going to try and kill you on sight or is more of a good guy, also if capturing him will make you rich icly.
I mean I highly doubt every nin, knows every other nin alive. The use of a bingo book would allow them to slightly stalk them if given an encounter. Only just a thought here. Would be interesting though to implement bounties with the bingo book, only really thought of it mid way writing this so, open to suggestions!