Bartering is a tricky discussion. Yes, it definitely applies when you are self-employed and do a job that you would charge anyone else for, but what if you are helping a friend in your spare time? If you receive something in exchange, the value of the item you received would be your income, but what if you don't receive anything in exchange?
If the company bought a computer that they loan to you to do occasional work for them, there's no reason you couldn't take the computer home and have that company retain ownership of the property. They could still expense the depreciation of the computer without giving it to you. If it were a car though, you would have to count mileage for personal use as income. What if you exchange occasional tech support for the use of an empty desk and Internet connection? As long as they aren't renting desks for money to others, there's probably no additional marginal cost to them if they allow you to use the space, so the fair market value question breaks down.