The subversive bacchanal for San Francisco’s eccentric underground is ageing out amid an influx of the super-rich

Burning Man, the infamous arts festival in the Nevada desert, turned 40 this year, and it’s showing some distinct signs of middle age.

It’s not just the tech billionaires who show up to party, the chartered flights straight to the desert or the HBO documentary about behind-the-scenes power struggles. The tens of thousands of people who assemble each year to create a tent city in the wilderness appear to be growing older, and it doesn’t seem that they’re being replaced by as many younger “burners”, as festival participants are called.

Three little letters - bnb-side’s name is a play on the local b-side arts festival, but Silicon Valley colossus sees threat to global brand

In one corner is bnb-side, a six-room bed and breakfast on the Isle of Portland – a tiny wedge of limestone tied by a narrow ribbon of shingle to the Dorset coast – that was created to help secure the future of the rock’s much-loved arts festival, b-side.

On the other is Airbnb, the San Francisco-based booking colossus. The battle between them is over the three little letters they share.