I'm not a member of one but I do operate as if I was sometimes. I do a lot of work for people in exchange for them doing work for me if they want to. The recent house move I did from Inverness to West Yorkshire will return me a website and training in how to set up and manage it. I organised a loan for a friend to go on a massage course and it got me free massage for life on demand. I am building a sound proof recording studio in return for roofing and plastering on my own house.
The sorts of things I do would be driving, transportation, some building trades, provision of firewood, housing and design consultancy, dog/cat/child/house sitting, and occasional escorting duties.
Organised schemes often go wrong for some people who have a high demand service to offer (usually trades) and who don't need much in return. Also other people find that there is little demand for their services (tuition in underwater basket weaving) and so they never get enough credit to get what they want.
