There have always been people who would break stuff or fail to return it, but their neighbors quickly learned who they were, and excluded them from the group. This was a powerful pressure, and people would not go against it for trivial reasons.

The social structures that supported the system used to be universal--every culture had them--but they've all but disappeared in middle-class America. It makes sharing a more risky activity.

Still, I think it's worth working around the edges to bring these systems back. The advantages accrue not only to the individual (who doesn't have to invest thousands in stuff he can borrow), but also to his neighbors (who have similar savings).

Beyond that, there are further wins. There's an economic boost: Everybody saves, so everybody has more money to spend and invest in ways that benefit themselves and the community. There's also an environtmental boost: Less stuff gets made (because what stuff is made is shared) which means less energy used, less raw materials used, less pollution produced, and so on.

Sharing, if supported by the necessary social structures, is probably the best way to boost everyone's standard of living.