Here's one hilarious story of a man, a hot yoga class that was not so hot, and a mat, as shared in his original Seattle Craigslist ad:

Yoga mat for sale. Used once. - $1 (Bellevue)

Yoga mat for sale. Used once at lunch hour class in December 2009. Usage timeline as follows: 

11:45a
Register for hot yoga class. Infinite wisdom tells me to commit to 5 class package and purchase a yoga mat. I pay $89.74. Money well spent, I smugly confirm to myself...