Hopefully they can add high availability clusters in regions other than US East (which is the only region which has high availability clusters right now).
Found-founder here. You can pick HA in eu-west-1 as well, and we've been battle testing a solution for other regions for some time now, and it'll soon be generally available.
The issue is that a lot of regions only have two availability zones, and having a third is important to prevent split brain scenarios. (Our solution to that involves using ZooKeeper.)