Not necessarily a new concept but the rise in these kinds of services are certainly showing us that people are getting tired of the fees being charged by systems such as PayPal and Ebay. Sites which bring sellers and buyers together in direct trade. Examples of this include Craigslist and Zaarly, and essentially they work by a buyer or seller posting what they want or want to sell and allowing sellers or buyers contact them directly. They encourage local transactions so shipping is not usually necessary as well.
The rise in such services I believe point to major happenings in the economy, the reduced buying power of the Dollar, these sites are thriving on the fact that a person can acquire new or used goods at a significant reduction in cost as well as the ability to use all of your buying power on the good or service desired instead of having to spend on unwanted services, such as the use of pay pal and shipping expenses. In order for a consumer to stretch the power of their money they are cutting out the middle men and trying to connect directly to the suppliers of what they desire. The only real downside is the scam customers and sellers. As an example my wife and I put out a posting to rent a room or two, we don't need to do this but we have a large house for us and it would be a way to improve our ROI (Return on Investment) in our home. We chose to do this because we are in a unique marketplace where rent rates have jumped up dramatically to the point where buying a house has an unarguably reduced cost of ownership. We had 5 replies, and only 1 of them was legitimate. Fortunately the scams tend to be easy to spot. The key is to deal locally, directly, and in cash. Most of the scams involve wiring funds or with entities claiming to be from foreign countries and needing transactions through third parties.
Another re-emerging market place for the same reasons is the local farmer's markets and butchers, these markets often see higher quality and healthier goods at comparable if not better prices than most local grocers. The great advantages come from reduced transit costs, reduced/non-existent middle man mark-up costs and near to no expense in advertising costs. However, one loss in certain goods can be in government subsidies, which your taxes and national debts are paying for, and as we know the national debt is another indirect tax in that it reduces the spending power of the money you have. [I personally think it is better to loose the subsidies and go locally where possible because I can still get comparable prices, support local small and mid-size agriculture and I feel the subsidies are hurting the global population to begin with as they distort proper supply and demand... so I say opt out of the system when you can] Additionally, to offset expenses and stretch the money consumers have I see more and more people turning to growing small back yard gardens as well. My neighbor has a small orchard even, instead of growing greenery trees they decided to have pear trees and the like, my grandfather for years has grown a garden in his yard and even sells some of his crops in their local farmer's market. In these cases the goal was not to become 100% self-sufficient, but to augment their food usage with higher quality and lower costing food. A close knit community could even put specialization to use, a neighbor grows tomatoes and another potatoes and they trade a portion of each among themselves.
The final reason and quite possible the most significant that is encouraging people to do this is an unconscious decision to cut ties with the global market place, the cost of shipping alone is making that market place more and more unattractive every day. While it is possible to get cheaper labor in developing nations around the world to meet the demand for the goods that you might find in the emerging market places above it is heavily burdened by the shipping services and fuel costs which they pay to move the goods here. In the end what you need to do is go and compare a little on what there is to offer, some keys to look for are what goods are grown and manufactured locally and naturally (if you don't live in a tropical state and a local farmer is selling pineapple... you'll probably be paying a premium since it would need heavy use of green houses and extra watering for example) and try to develop a personal relationship with them... a local merchant is MUCH more likely to barter or negotiate prices with you than the mega store especially if you are on a first name basis with them and often they could provide insight on how to do some things yourself if you choose to do that.... my parents even got a great recipe for spaghetti that uses spaghetti squash instead of noodles from one of their local farmer's market merchants... it was really good!
What kind of experiences have you had with local market transactions?