Markus (5/9/2012)
Do you control the backups/restores? Is SQL Server patched automatically if a service pack or security patch comes out? If so, and it causes issues with your application how do your roll it back?I just do NOT like the thought of all of my data in the cloud where I have no idea if anyone else has access to it and I have no way of knowing this.
You can specify if you want patches applied automatically, and you can specify a backup window. They do a quiesce of writes and a snapshot of the server. They also do log backups and point in time recovery is available. Jeremiah Peschka wrote on it here: http://www.brentozar.com/archive/2012/05/sql-server-rds/
Please don't worry about someone in Amazon accessing your data among their thousands of virtual machines. It's much more likely a co-worker or friend gets access to your machine and takes the code/data if you get popular.
Plenty of companies, popular ones, have code and data in the cloud. I would not put financial, medical, PII info up there, mostly because of liability, but there are lots of apps where it would work fine. Like SQLServerCentral.