It's required to work at all, not just as some kind of guard rail. It's like the oil in a normal bearing, the oil isn't just to prevent a crankshaft crash in case the car is jolted while in operation, the oil is a part of the way the thing functions at all in the first place.

Also, you could imagine a magnetic bearing whose field strength rapidly diminishes as you move away from it, due to cancellation, like a Halbach array [0]. I wonder if there's a simple geometric configuration for a bearing that has this property, as well as the critical property of passively stable levitation, maybe based on diamagnetic or superconducting materials [1].

edit: Maybe something in this direction? [2]

[0] https://en.wikipedia.org/wiki/Halbach_array

[1] https://en.wikipedia.org/wiki/Magnetic_bearing

[2] https://ntrs.nasa.gov/api/citations/20070006849/downloads/20... ("Development and Testing of a Radial Halbach Magnetic Bearing")

So write too many zeros to your drive, the disk becomes demagnetized, and the head will crash?