So I figured I'd try to think about some immediate obstacles to setting up an anything library, or a usufruct (thats me trying to coin a more elegant name).
One thing that comes to mind: how to stop randos from taking stuff and selling it. Sure this might not be a problem in a post-scarcity society where resources are distributed well and people know their neighbors, but right now we aint living in that.
A solution might be to make private usufructs first, exclusively for members of an affinity group or neighborhood, and have some security to stop outsiders taking things. Its not pretty, but might be necessary for getting the library economy off the ground.
Another problem is where to store things. Where to put a usufruct? Buildings aint cheap, whether rent or mortgage. Especially in cities. My thoughts were maybe not having a physical usufruct in the beginning at all. Have a site in which stocks can be listed, and people simply stop by each others houses to pick stuff up. No capital needed.
@phneutral@feddit.de had a similar idea, although I'm skeptical of having it completely open (at first) and attaching any kind of points/rep based system onto it, i.e. likes. Reputation is obviously important to any social system, but I think humans do a far better job than an algorithm or formula. However, maybe they had a different purpose in mind for likes on such a system.