For that level of Page Views you want 1, maybe 2 dedicated servers (1 web, 1 database) with fast disks - SAS RAID10 recommended. You will start to run into database performance issues with that level of PV, most won’t support the heavy I/O that it will have.
As you well know (running a hosting company), no service can guarantee 100% uptime.
As people try to save money using cloud service by using inexpensive, low latency network connectivity between zones; however although this saves money it is an inherent risk as opposed to people duplicating their web sites in each region. This zone based hosting comes with some types of access problems. DB’s for example, can be really bad if their stuck in different zones; not to mention the ‘what happens if a hurricane hits region X,Y, X’. When networking, hardware routing, and or too much mirroring bandwidth clog up zones this approach can be less than 100%. It still however offers people a way to do it so they can afford it, that they otherwise may not if choosing a traditional host (in all of their worldly locations).
Non network connectivity between zones types of hosting should always be more stable, but doesn’t offer the same promise of spreading the latency (at a low cost) between the zones.
It kills me as marketers branded ‘Cloud Hosting’ and many seemed to forget the fact that there is still networking, blade servers, cabiling and possibly clustering technologies and wireless technologies that have the same potential to fail as they always did. All cloud has allowed us to do is to spread around risk, but it doesn’t eliminate it.
I’m certain that your service runs well and that you do very much know what your are talking about. My only point is that there may be different reasons that someone scales up a service in Amazon or Windows Azure as they may be happy with the pricing and the service most of the time and can deal with the types of service outages come with the territory. Otherwise someone should look at hosting in a less complicated environment that has a better chance of overall stability.