By default this option is turned off. When you load the mod menu, the value you see displayed is the setting currently in use in your game. The vanilla value is 2.0, so any other number indicates that another mod is already changing this setting. If you decide to turn this option on, than the settings from Trade & Barter will overwrite any changes to this value made by other mods. If at any time you wish to revert the settings back to those made by another mod, simply toggle off this option and reload your game. You will need to reload your game before the changes from Trade & Barter are fully canceled out.
Anthropologists have argued, in contrast, "that when something resembling barter does occur in stateless societies it is almost always between strangers."[6] Barter occurred between strangers, not fellow villagers, and hence cannot be used to naturalistically explain the origin of money without the state. Since most people engaged in trade knew each other, exchange was fostered through the extension of credit.[7][8] Marcel Mauss, author of 'The Gift', argued that the first economic contracts were to not act in one's economic self-interest, and that before money, exchange was fostered through the processes of reciprocity and redistribution, not barter.[9] Everyday exchange relations in such societies are characterized by generalized reciprocity, or a non-calculative familial "communism" where each takes according to their needs, and gives as they have.[10]
If you've ever swapped one of your toys with a friend in return for one of their toys, you have bartered. Bartering is trading services or goods with another person when there is no money involved. This type of exchange was relied upon by early civilizations. There are even cultures within modern society who still rely on this type of exchange. Bartering has been around for a very long time, however, it's not necessarily something that an economy or society has relied solely on.
I wish I came up with this fantastic idea. SharedEarth is a free site that connects landowners with gardeners and farmers in need of space to grow crops (i.e. starting a home vegetable garden). You can find free access to land in exchange for sharing a little bit of produce with the landowner. In a time of a strong and growing local food movement and concerns about food safety, SharedEarth might just be the most important sharing site of all!
While it may be free, there is no one monitoring the barter ads, so you must be aware of potential Craigslist scams, and realize that you are always at risk when it comes to meetups and exchanges. For example, about a year ago, I arranged to trade massage gift certificates for housecleaning. Since the individual was coming to my home, I was more nervous than usual. However, she offered good previous references, and we  arranged for a time to meet when my husband would be home, in case an odd, unexpected, or even dangerous situation arose.
He would have heard of channels and sandbanks, of natural features of the land useful for sea-marks, of villages and tribes and modes of barter and precautions to take: with the instructive tales about native chiefs dyed more or less blue, whose character for greediness, ferocity, or amiability must have been expounded to him with that capacity for vivid language which seems joined naturally to the shadiness of moral character and recklessness of disposition.