Currently the org.apache.cassandra.locator.Ec2Snitch reports "us-west" in both the oregon and the california data centers. This is incorrect, since they are different regions.
California => us-west-1
Oregon => us-west-2
wget http://169.254.169.254/latest/meta-data/placement/availability-zone returns the value "us-west-2a"
After parsing this returns
DC = us-west Rack = 2a
What it should return
DC = us-west-2 Rack = a
This makes it possible to use multi region when both regions are in the west coast.