Rackspace made headlines recently for having multiple outages.
My first startup was a hosting company -- my partner still runs it and I exited a few years ago. Having "been there and done that," I have a lot of respect for anyone that can stay in the hosting business -- when everything is running just fine, your customers are complaining about why things can't be cheaper. As soon as the network blips for even a second, everyone's talking about how crappy the network is, why they pay so much (even on $10/mo accounts), etc.
In other news: it's early, I can't sleep and I might be a little cranky. :)
That said: my point wasn't so much that Rackspace is a bad hosting company, but rather that the original question was looking for a solution that would offer really close to zero downtime for their customers, and given that, "put it all on Rackspace" isn't a viable answer.