http://en.wikipedia.org/wiki/Pu-erh_tea presents an interesting treatment of the subject. Note the following, copied from the article:
"Poor control in fermentation/oxidation process can result in bad ripened pu-erh, characterized by badly decomposed leaves and a flavour and texture reminiscent of compost."
"Poor control in fermentation/oxidation process can result in bad ripened pu-erh, characterized by badly decomposed leaves and a flavour and texture reminiscent of compost."