I must say that announcing a players position with out decent reason , is not cool at all.
I can however see it as a good strategic move, if I am about to be eliminated or want to distract players from another part of the board, that I am going to make a move on.
One must remember that players do not know if what the guy is saying is true, the only way the other players would know it, is if you acknowledge that the guy is correct.
I have seen many players use the chat to convey false info in a FOG game, and any experienced player would think twice b4 believing game chat in a FOG game.
