I have one, but I call it a trash compactor bag - it's white, lines my pack to keep the stuff inside dry, and lays out flat on the ground so I don't lose little stuff in the pine needles/leaves or get stuff muddy. It also makes a great place to stand in stocking feet when getting into or out of the hammock.
"In the beginner's mind there are many possibilities. In the expert's mind there are few." Shunryu Suzukihttp://hikeandbackpack.com