According to this calculation (which attempted to probe all the racks in EC2), over 70% of EC2 lives in us-east.

http://huanliu.wordpress.com/2012/03/13/amazon-data-center-s...

I'm under the impression it's the most used.

It probably is the most used, being a cheaper alternative to us-west, but are you suggesting it fails more because it is used more? It does seem that the big AWS outages (in the us) have been concentrated in us-east. I have wondered if it just because us-east is newer so they haven't had has much time to work things out, or that the us-west team is a little better?

edit: btw, I am not dismissing "used more" as a valid theory. More use = more hardware = more complexity which could lead to more failures.

There are two different us-west regions. One in Oregon (priced the same as us-east) and one in California.

My theory is "used more".

It's the oldest, yes.