Having a collection of servers that act as transaction clearing houses for people would probably work but it seems to break the whole p2p idea of the system. And I think isn't necessary if you design the system right in the first place.
It depends on how it was implemented. I don't think having transaction clearing houses necessarily excludes p2p. It depends on how the network was implemented. Assuming things remained open, the transaction clearing houses could still be p2p. Anybody could join in and work to clear transactions. It's just that it wouldn't be required in order to send/receive transactions. It would actually be extremely beneficial if there were literally thousands of transaction clearing houses or if some regular users did participate in the full system to prevent the established clearing houses from conspiring together to cheat the system. That is one of the beauties of bitcoin IMO.
It seems like the best thing would be to lay the system on top of a DHT like kademlia. Maybe you can do this later I'm not sure. Again the documentation is lacking so it is hard to tell if you can easily break the chain apart in order to stick it in a DHT later. I was hoping the devs would stop by and answer maybe they are too busy improving the docs...
Although DHT is an interesting concept I don't know if it really solves the problem. Smartphones are a good use case:
- You don't want to be acting as a peer on a p2p network with a smartphone. It hurts battery life and it could be costly in cellular data charges.
- Smartphones don't have the processing power or storage capacity to either process blocks or store even parts of the block chain.
The future is not desktop PCs but is "thin" machines like smartphones, tablets and netbooks. These lightweight devices will vastly out-number PCs in the years to come. It isn't tenable to participate in p2p from a thin device, at least in the forseeable future. I think Gavin's ideas of a lightweight bitcoin client seem to address this issue.