Caution: This is kind of icky.
When I was recently married, some people threw out an entire living room set of couches (a big couch, a love seat, and a matching chair).
We were thrilled, and waited for cover of darkness to move them all into our bare tiled livingroom. There were kind of damp, but since it had been a very humid day we weren't too worried about it.
We got them inside, and noticed that they smelled bad. No big deal, some carpet cleaner or something would help out.
We left them there over night, festering...
When we got up the next morning we went to the living room to check out our new furniture, only to discover that bugs were all over it, and under it, and in it.
And now they were all over our house.
We didn't know it, and didn't find out until several weeks later that the landlords had thrown the furniture out because they evicted the owner. Evidently the place was so filthy they weren't able to get work crews to come in to fix the place up until they had torn out most of the walls and flooring. (I wonder what that guy was into to this day...)
Moral: One mans trash is another mans treasure. But if it is already in the trash, you can have a pretty good idea of what it is supposed to be...