Which subjects are taboo for the writing industry? Some say same sex relationships, some won't publish stories involving the creation of offspring, and for others it's animals or siblings. That isn't to say there aren't houses which will publish the taboo topics, you just have to look for them.
My limit is animal love. I don't understand it, don't wish to, and wonder at the sanity of any who are involved in the reading or writing of that profanity. Where is your limit?