Economists since the times of Adam Smith (1723-1790), looking at non-specific pre-modern societies as examples, have used the inefficiency of barter to explain the emergence of money, of "the" economy, and hence of the discipline of economics itself.[3] However, ethnographic studies have shown that no present or past society has used barter without any other medium of exchange or measurement, nor have anthropologists found evidence that money emerged from barter, instead finding that gift-giving (credit extended on a personal basis with an inter-personal balance maintained over the long term) was the most usual means of exchange of goods and services.[4]
Kids sure do grow out of their clothes rather quickly, and that’s where ThredUP comes in. They set up a cool shop for parents to swap clothing and toys with other parents whose kids are different ages. You can pick up a box full of clothes or toys for just $5 plus shipping, or post your own child’s used clothing for other users to pick from. Membership is free for everyone.
As Orlove noted, barter may occur in commercial economies, usually during periods of monetary crisis. During such a crisis, currency may be in short supply, or highly devalued through hyperinflation. In such cases, money ceases to be the universal medium of exchange or standard of value. Money may be in such short supply that it becomes an item of barter itself rather than the means of exchange. Barter may also occur when people cannot afford to keep money (as when hyperinflation quickly devalues it).[15]
Can you teach a skill like canning or cooking from scratch?  Food staples will be more readily available than the processed food many are used to buying at the grocery store and fast food.  And although many in the preparedness community know how to can and cook from scratch, your common everyday American doesn’t.  They wouldn’t know what to do with flour, eggs, and a little oil.

It is said that “Necessity is the Mother of Invention.”  If we ever get to a point where a barter economy is the way goods and services are exchanged, things will come together.  But those who are prepared ahead of time, those who have thought about all of this, will be in a place where they can quickly move to make decisions that will benefit themselves and their family financially.
^ Homenatge A Catalunya II (Motion Picture). Spain, Catalonia: IN3, Universita Oberta de Catalunya, Creative Commons Licence. 2010. Retrieved 2011-01-15. A documentary, a research, a story of stories about the construction of a sustainable, solidarity economics and decentralized weaving nets that overcome the individualization and the hierarchical division of the work, 2011.
Zipcar has been renting cars by the hour or day for years now, and they keep adding to their list of participating cities. You can pay different membership and rental rates, depending on how frequently you think you’ll need a Zipcar. Though the process varies, you basically sign up in your city, pay the application fee of $25 and any annual fees (ranging from $0 to $60, depending on the plan), and voila – you can now borrow a Zipcar for an hourly rate or daily charge. The rental includes gasoline, auto insurance, and 180 free miles, which is usually plenty.

When barter has appeared, it wasn’t as part of a purely barter economy, and money didn’t emerge from it—rather, it emerged from money. After Rome fell, for instance, Europeans used barter as a substitute for the Roman currency people had gotten used to. “In most of the cases we know about, [barter] takes place between people who are familiar with the use of money, but for one reason or another, don’t have a lot of it around,” explains David Graeber, an anthropology professor at the London School of Economics.