Barter-based economies are one of the earliest, predating monetary systems and even recorded history. People can successfully use barter in many almost any field. Informally, people often participate in barter and other reciprocal systems without really ever thinking about it as such -- for example, providing web design or tech support for a farmer or baker and receiving vegetables or baked goods in return. Strictly Internet-based exchanges are common as well, for example exchanging content creation for research.
Yes…yes…yes! When I went to school to become a Registered Massage Therapist, and discovering how difficult it (still) is for a male RMT to get a legit job be it here or a small town, our instructor told us to consider bartering whenever possible. This was in a smaller city (100,000) where bartering can do well for you to make inroads with the Downtown Council, locally owned businesses; let’s say for example a new yoga studio or health club or salon is opening. I bring my massage chair over and do free 10 minute chair massages and give out my business card, in exchange, the yoga groups can use my space if they need to add an extra class. The salon knows if they’re doing a training on a day I’m not working, they can use my studio. Things like that.