At least for the relatively small businesses that I deal with, I basically always recommend to save the effort that would go into building a 'highly available' system, and instead spend it on a scenario for keeping the business running when tech fails—which it will to some extent at some point, no matter what. I suppose that line of thinking would do wonders for much larger businesses as well. When a system becomes too important, rather than trying to make it even more reliable, try making it less important first.