Look at it like this, If you have a friend and you do each other favors and buy each other beers and lend each other money then that's perfectly fine and dandy and the IRS has no cause to get involved in any of that. This is perfectly legal and the way it should be.

On the other hand, if you have a business that mows lawns and you move lawns for 10 different people and you run a bartering scheme with them then you should declare for the value of the bartered service.

Now, what if you're in a group of 10 close friends and you don't have a business but you like helping each other out. One of your friends has a kick-ass yard lawnmower, the other has a chainsaw, the other has a wood cleaver and so forth and you just like helping each other out since you've found that work better as a team. Great right? Well, now of them is going away on a business trip and can't make it to the collective yard day so instead he'll tell his friend he'll do his bit when he comes home later. And to remind everyone not to forget they have a free one coming he gives each of his friends a baseball card.

The above is still perfectly legal but can you see where this gets tricky? How do you define "friends" and not "business" and how do you prove that someone isn't a friend but in fact run a pure business. What if you expand the circle of friends to 100? 1000? 10000?

My point is merely that when you really get into it taxes are fuzzy, as are so many other things things.