Google wave is an example of what works well with a central server: you have many documents that can be sharded across many instances because each document only

Google wave is an example of what works well with a central server: you have many documents that can be sharded across many instances because each document only needs to be consistent with itself, and your throughput limit is therefore only per-document which is more likely to be bounded by the number of participants that can practically interact in a single document. There is still the issue of a node becoming hot because there is an unusually active document on that node, which would usually not happen in a completely decentralized model.