What are the negative effects for a male who humps pillows daily?

Humping a pillow is nothing more than masturbation. Other than the hygiene issues of the pillow, not a big deal. Most humans and many animals masturbate. Done in moderation and not to the exclusion of other interpersonal relationship's it is very common and by most consensus normal, sexual behavior.

Done to excess or to the exclusion of other important activities like getting a job or interacting with friends or family it could be antisocial and psychotic behaviour.