I regularly share films and CDs with my friends - y'know, the old fashioned way, I lend them the discs. I do the same periodically with books and would with PS2 games if I knew other PS2 owners.
I would happily do this on a larger scale. Quite simply, though, the process of identifying friends who
would like to borrow items that I posess and would be willing to loan is tortuous.
However, I also build online library systems for my job. So why not combine them?
So, imagine a website. You register as a possible lender, giving basic personal details and a categorised catalogue of items that you are prepared to loan to others.
Friends may then invite you (or you them) to join their 'network'. You may then browse an anonymous catalogue of shared items (minus anything you're listed as owning). If you want to borrow something, place a request, optionally saying when and for how long you want to borrow the item for.
Any of your friends who have the item are then e-mailed the notification that you've asked for it, which is recorded in the site's back-end. Your friends can then log in and decide to grant, ignore or delete the request.
If your request is granted, an agreed timeline is placed on the item and it's up to the friends to pass the item between them. As soon as one loaner grants a request, it disappears for all others and they're (optionally) notified of this. If all loaners have deleted the request or it's time-limited and that's passed, it also goes and the requester is told.
You could then monitor the status of your collection and user status, showing how much they lend v how much they borrow, reliability of getting loans in and out and that sort of thing. As with eBay, if someone damages your stuff you can put a negative feedback mark against them. So, friends can work out based on shared experience whether they really want to lend something to another friend or not.