Amazon RDS (MySQL server service) now provides hot standby replication
developer.amazonwebservices.com
developer.amazonwebservices.com
Amazon has a good story for replication, now with RDS across availability zones, and Elastic Load Balancing, etc.
I am helping a customer with some large scale AI/text mining, and I think that they will also have me help set up a split internal data center - and AWS for overload and failover. AWS is a great deployment platform, but it does take a lot of effort to use it for projects that can't just use a platform as a service provider like Heroku.
I find $80 cost-prohibitive when considered in the context of a side project that I'd like to try out.
If AWS had a cheaper, less powerful option, I'd use it in a minute, because I really like their how their pricing scales and the feature set they provide.