Suppose you send out a tweet to all your friends: "Need help loading moving truck. Free pizza and beer for all volunteers. Call me."
Five or six friends show up, help you load your truck, and eat your pizza and drink your beer when the work is done.
Have you just engaged in a bartering transaction? Do you have to report the FMV of your friends' labor as taxable income? Do they have to report the FMV of the pizza and beer as taxable income? Why or why not?