alkalai dust

In the lastest issue of Jack Rabbit Speaks, the Burning Man newsletter,
someone wrote:

> Bring a beat up bike. (the alkalai dust will trash your nice one)

Does anyone know what the real danger is here?

I’m planning on bringing my (standard) Miyata to Burning Man. I could buy a
crappy uni from a local bike shop, but the thought of riding a crappy uni for a
week isn’t that appealing.

Does the standard Miyata have sealed bearings? If so, I’m not sure what could go
wrong. I imagine any uni is less vulnerable than a bike, but I don’t know what
the issue is with bikes.