I don't think this wonderment really applies to non-dedicated hosting (however awesome Slicehost might be). When dealing with shared hosting of any sort (VPS included), it's a reasonable assumption that the host will stay fully on top of hardware issues, since you are not paying for a physical box.
If something craps out in one of my dedicated machines, I'll alert the host or NOC to have the fault looked into and fixed. If something craps out in a box hosting my home directory or VPS or what have you along with numerous others, I already expect that to be automatically detected and fixed within an acceptable timeframe. Ideally, in a VPS environment, my machine(s) should be migrated to a working box in the interim.
If something craps out in one of my dedicated machines, I'll alert the host or NOC to have the fault looked into and fixed. If something craps out in a box hosting my home directory or VPS or what have you along with numerous others, I already expect that to be automatically detected and fixed within an acceptable timeframe. Ideally, in a VPS environment, my machine(s) should be migrated to a working box in the interim.