There was a story a while ago when IRS went after someone who was fixing their friends' and neighbours' cars and didn't ask for money in return. He was retired and he liked working on cars and he did it for free. IRS claimed he should have reported it as income.
In respect to money being a measure of wealth, was he "theoretically" becoming wealthy and acruing "good will". Later by changing his mind and asking for favors from his neighbors he could "cash in" his "good will" but avoid paying income and sale taxes on it.
How did the IRS get on this guy's case? There's no paper trail. I find it hard believe that one of his friends or neighbours went to the IRS and said, "This guy fixed my car and didn't charge me! You'd better investigate him."
I'd say those bartering services are definitely a gray area or illegal because they avoid the taxes. But that they even caught on to the accrued good will seems impressive.
Edit: don't shoot the messenger, I did not create the laws
In respect to money being a measure of wealth, was he "theoretically" becoming wealthy and acruing "good will". Later by changing his mind and asking for favors from his neighbors he could "cash in" his "good will" but avoid paying income and sale taxes on it.