As luck would have it...

I've just found an article by Alex Steffen on worldchanging.com on Use Communities which discusses the idea of sharing stuff between people, as an alternative to buying multiple copies of the same thing (which might remain unused). I’ve made a comment here (scroll down!).
John Thackara also writes well on these topics in his excellent book In The Bubble.

I really like these ideas. What is interesting is implications for the kinds of IT systems you might have to support sharing of things— reputation based systems (like ebay) that could help to create trust between members of the community, logistics systems to track the items… These kinds of systems might not be particularly necessary for informal networks such as small community groups but could be needed for larger networks where people would not know each other that well or at all.

In this way you can get around problems such as people returning stuff in bad condition (they get rated as such) and locating lost items and so on. You might even get some positive side effects—people get to know others in their neighbourhood and build up trust in them; or negative ones—some loss of privacy.

But the question remains, what kinds of things would people share, and how could it be done in an economically as well as environmentally sustainable way? The answers will be specific to particular geographies, demographies and cultures and the type of thing to be shared, among whom and how acutely they need it, will drive the particular solution. We need marketers who can divine these hidden needs and make them explicit… whether for private or public good (or both). It will be interesting to see where and how it succeeds.