Any idea why that's pegging the CPU? My naive analysis would be that once the database has sent/stored the data, the server is just doing some light filtering/serialization and sending it off to the client. But obviously there's more going on if these requests (en masse) can get you to 100 load.
Shot in the dark: Is there some kind of sorting going on?
ajax/get-accounts
ajax/get-streams
ajax/get-other-settings
ajax/store-client-view
ajax/get-tweets
ajax/sync-relationships