The gist that I'm getting from a few places seems to be: Have separate hosts/service providers, and do the load balancing yourself, or make switch yourself, when one fails. I've yet to find many detailed examples, though, as most similar articles deal with load balancing with in your own locally-managed network, or co-located set of machines.

The more generalized "Cloud plus Dedicated" fallback/load balancing seems fairly involved, and raises a lot of other questions, but at least I've got a path to follow now. Also would be more expensive, as a backup server might just be hanging around doing nothing at times.

Then again, it would pay for itself in satisfied customers after just a single event.