The "sweat" aroma is often from a yeast called brettanomyces bruxellensis. Some people say that it causes flavors that suggest horse sweat. It can consume sugars that normal beer yeast cannot, so it can infect finished beer and make it rather funky. It is quite fashionable right now to add it deliberately. Many Belgian beer styles call for some Brett character.
Our brewer at Third Street is fond of the funk. He is opening my eyes to all kinds of new things.