I don't see where that Sec even refers to commercial pilots as the heading reads:
"Private pilot privileges and limitations. Paragraph (b) simply states "A private pilot may, for compensation or hire, act as pilot in command of an aircraft in connection with any business or employment if: etc.
I know what people may think this implies, but nothing is mentioned here about holding a commercial certificate. SOme may have "heard" that it does not pertain to being paid for services, but it certainly seems to say that to me. What would be the point of even putting this in if it were not a stimpulation that states when a Private pilot may be compensated.
A private pilot may get paid for doing work that involves flying airplanes. Airplane sales, repair station work, flying to a business trip and getting paid your regular rate all qualify under this exemption.
The difference is if you're going to be paid to be a PILOT (as opposed to being a salesman, engineer, repair station worker), you need a commercial certificate.
Ferrying airplanes, where someone asks you to fly their airplane for them, means you're providing PILOT services, and thus requires a commercial cert. And while it's perfectly fine for a PPL working for a repair station to pick up your airplane to take it to the shop, and bring it back, it would NOT be ok for him to take it from one place to another place not in conjunction with the repair work that is being done for you. It's also not legal for a repair station to hire a PPL AS A PILOT. The PPL can be a mechanic, an avionics tech, a manager, probably even a janitor, but his primary job cannot be flying.
And as Henning says, insurability is a whole different story. I know of dumb private pilots and cheap owners who hire them to ferry their airplanes, and as long as nothing goes wrong, they only have to worry about the FAA hearing about it and pursuing a certificate sanction. Bend the airplane and they'll be looking at that plus all the financial fun of probably not being covered by the insurance, which means no coverage for the loss of the airplane, injuries, or god forbid the carful of nuns you crashed into.