My understanding was that SF already had a fairly strong datacenter backend. Or is that not the case? By doing this wont they be restricted to what the GAE ca

My understanding was that SF already had a fairly strong datacenter backend. Or is that not the case? By doing this wont they be restricted to what the GAE can functionally provide like: - Python only support (with Java and Rails coming soon), - other technical limits or is that a "small" cost to pay for the kind of scalability they cannot provide themselves any time soon?