Just to be clear. DotCloud is in fact designed to withstand instances randomly crashing.

So far however, it has not been designed for instances randomly crashing across multiple datacenters. I will add that neither is the canonical high-availability designed recommended by Amazon.

Why not? That's the whole point of cloud computing, that you can cater, or have to ability to cater, for situations like this. If you don't take advantage of those abilities, well, then thats is something you have to sort out with yourself.