A recent podcast on the IT Conversations network is very interesting. It is a speach given by Werner Vogels, CTO of Amazon.com on the difficulties and potential for scalability. In the speach he states an interesting fact about Amazon's internal service orientated architecture:
"It's not a matter of buying bigger databases... If you go to a page in Amazon it will go out to about one hundred to one hundred and fifty different services and build the page out of that."
Wener Vogels - Scalability, IT Conversations, 12:40 to 13:00 into the podcast