"A traditional backpacker might also include durability and ease-of-use, but I'd argue these are less important to lightweight hikers."
As part of my sleep system, durability is an essential element of design that I look for in a sleeping pad. Perhaps more so in the lightweight world than in traditional backpacking. I recently switched from the torso lite pad for this very reason. Perhaps on a short (>=3 day) trip it doesn't matter if your pad become a self deflater, and in that case maybe one could go without a pad at all to save even more weight, but on an extended trip, with multiple high mileage days in a row, a good nights sleep can be part of risk management. Additionally, without the added insulation of a sleeping pad, many lightweight sleep systems can be easily pushed beyond their useful threshold. In January of this year my self deflating torso lite dropped the effectiveness of my prototype (and admittedly under filled) GoLite quilt from barely comfortable (about perfect, because I had to wear all my cloths) to down right frigid and miserable.
Propagating the stereotype that lightweight gear is or has to be delicate is not helping the lightweight movement gain any momentum in the industry. Certainly there is a balance and trade offs that must be made, but dismissing durability as less important seems to support a consumeristic and disposable culture that I find conflicts with any notion of being greener. It goes REDUCE, REUSE, RECYCLE for a reason.