As a PFS player of a true-neutral cleric with a true-neutral god, I was surprised when a GM at an event informed me I was now "evil" at the end of the adventure, because I'd cast deathknell on a fallen demon (no less). Atonement was required to play the character further, and it was marked on my chronicle sheet, etc. That was the only evil act in question.
Anyway, is this sort of thing entirely at GM discretion? I was under the impression that things like animate dead and deathknell were dangers for "good" characters. That performing a single evil deed would no more make a neutral character "evil" than casting a healing spell would make him "good".
All in all, I think spells that can only be used in the performance of an evil act should be removed from the game, if this is the right ruling.