William Sealy Gosset published a result under the pseudonym Student. (Because his employer, the Guinness brewing company, did not allow their employees to publish for fear of divulging trade secrets.)
Why isn't publishing under a pseudonym a breach of academic ethics? It seems that the common idea is that publishing under a pseudonym is ethical, unless they are deliberately used with intention to defraud or deceive. But, given that we don't know who a pseudonymous author is, how can his peers have any trust in that (or even check it)?