This company specifically forbids the use of their campervans at Burning Man, but it is good to know about these rental agencies if you would like to take a trip up and down the coast some day. http://www.californiacampers.com/
In reality, Burning Man is perfect for the bigger gas hog RVs because you remained parked for a week instead of driving around burning gas.
On a side note: While I was camping at Sequoia National Forest in my Toyota motorhome, I met a man who rented one of those monster motorhomes. He said that he went through $45 in gas just getting over the Grapevine from Los Angeles while I hadn't gone though that much gas my entire trip from Sacramento to Sequoia and driving around the park. Americans typically just don't do smart. Most Americans would prefer to go though a ton of money in a 5 day blow out in Cabo San Lucas than backpack for a month through the Mayan wonderland of the Yucatan peninsula and kick back for a week or two in Tulum. We have a cultural aversion to getting away from the job long enough to truly relax. That's good news for all the starving psychiatrists and family law practitioners out there who badly need our business. I would hope that the type of person who goes to Burning Man would be counter to the typical American tourist who wants things quick and wants things easy.