I think it is not bad to do so and not still bad not to do so because sometimes your friends already know the truth and are really ashamed to admit that you were right and they were wrong so rubbing it on their face may not really matter because next when you make a gambling decision and they're about to step against, like say their mind or impose their choices on you, they will remember that the last time you were right and they were wrong and maybe that may discourage them continuing. It may be surprising to you also that maybe these your friends will start consulting with you before they make their gambling choices and decisions.