What is happening in this thread is what I have seen before in these type threads. There is much confusion between us posters because we are mixing different areas of the law. In this case, we are talking about vehicle registrations (the license plates for the vehicle) and we are talking about licensing requirements (your actual driver's license). These are different, each has different requirements, and they don't neccessarily go hand in hand. I will be referring to the race car example, as that is what I am dealing with, and that is also what Robert was asking about.
My understanding is that if you are paid to race, you are commercial (and all that entails). There is a particular state trooper on I-80 in Illinois (somewhere near Dixon) that has a hard on for this very thing. I personally know of several people that he has pulled over. One guy has a big toterhome (registered as an RV) that pulls a big gooseneck race trailer. He got pulled over and shut down for not having a CDL. Even though his toter is registered as an RV, once he hooks up the trailer, he is commercial, and has to follow all of those rules and regs, CDL and all. As to Larry's comment about being not-for-hire, that apparently doesn't matter. You are engaged in an activity that is for profit, therefore you are commercial. Another racing buddy got hit by him a few weeks ago, and all he was doing was hauling a newly purchased car back home. Now his rig is smaller, so he doesn't need a CDL, but he was asked for his logs and such. He got away with a warning, but annoyed the trooper with all of his questions!!
Now, in my case I really don't want the hassle of the additional regs, but I can see the writing on the wall, so I will be getting a CDL and be as legal as possible. I'm still pulling with an F-350, so the commercial registration won't hurt me yet, but when I get a big truck I'll be all set. And hell, it certainly can't hurt to use that as an argument when the IRS tries to declare my racing business a hobby!!! Now if only there were an easy place to get all the neccessary info.
As for RV's (used for RVing), my understanding is that if you've got RV plates, you're good to go. But even there, some states are cracking down and requiring Class A or B (non CDL) drivers licenses.