I think the author is unaware of a great tool for scaling PostgreSQL. A few years ago Skype released plProxy and pgBouncer, both of which are key to PostgreSQL scaling. What they in essence do is allow for transparent horizontal scaling of servers. One defines a cluster in plProxy and then when you run stored procedure queries, they remotely execute on the proper shared server based upon the primary key data. It's fast and effective and I have been using it in a very large OLTP environment using PostgreSQL, driving a US Top-25 pageview site.
I should clarify, plProxy is responsible for the transparent horizontal scaling. pgBouncer is a proxy that allows you to run all of this using a minimal number of PostgreSQL backends, which is essential because of the amount of inter-process communication locking and information sharing in PostgreSQL. pgBouncer basically manages a smaller pool of active backends reducing the overhead in running high transaction velocity servers.
