Pure network-mediated barter has a number of issues, primarily that getting the numbers up to the critical mass point in a given geographical area is difficult, in large part because there's a non-trivial barrier to entry: being capable of dealing with eBay's submission and bidding process. Now, to most of the folk reading this, you're possibly questioning that, and also eBay deserves a lot of credit for making a fairly easy-to-use system. But, a) it's still too hard for large blocks of Joe Public, b) a lot of people will never trust the seemingly anonymous trading and c) there's a lot of lost potential in getting only one sale but from many people, but eBay's trust metric (in common with most trust metrics) distrusts new users, and for good reasons.
So, we need a proxy. We need people willing to sell your stuff on eBay, and along the way maybe they could buy you some cool things as well?
The Everything store is that solution. It's called that, because quite simply, it buys and sells everything (well, anything legally purchasable and anything it can persuade other people to buy). On the "sell your stuff" side, it would give money to customers for their unwanted goods (estimated eBay selling price + small commission) and sell them on eBay. On the "buy stuff" side, customers can come in (or order online) and request things they want to buy, the staff quote a price (again, estimated eBay price + small commission) and the item is either later delivered to the customer or they can come and pick it up.
There are a couple of practical implementation limits on this one, primarily that you'd need staff with expert knowledge on a lot of things. This can be reduced by making sure you've got a reasonably wide range of knowledge among your staff as a whole, plus potentially having a collection of experts on particular topics available by phone in order so you can figure what items the staff should offer $LARGENUM for as it's worth insane numbers.
This is the bare bones of it, but there's a couple of refinements that make it more interesting, both from a business sense and from improving its utility as a node in a barter system. The one that first comes to mind is that when items come in, they aren't sold on eBay immediately, but instead are displayed in the shop for say a week. At a trivial level, this better illustrates the concept of the shop to new customers, as this will probably end up being a very random collection of items. Also, these items would be purchasable by incoming customers (thus saving the times and fees of eBay for the store), and potentially the staff could be empowered to barter for items as well i.e. swapping things in the store for other things that customers bring in.
It's probably worth expanding beyond eBay as well, both in that having a single point of failure is bad (eBay is unlikely to actually fail, but notable changes in fees is not unlikely), and that also being willing to purchase from wherever (conventional stores included) allows for a more true notion of a "everything" store.
Not sure if this would ever actually work, but it does seem like quite a cool idea.