cengland0 (7/26/2011)
Running in memory scares me, ... ... I still think a large scale power failure could be disastrous, so I assume these products do write to disk at some point.
Depends on what type of memory. There are many different technologies. Some are non-volatile memory which retains it's state even if the power is turned off. The newer SSD drives are memory and will retain it's information during a power failure as well.
Azure is indeed a "VM in the cloud"; however, it is stateless. Azure Storage Services offer you two choices of persisting your data: either in a fully relational SQL Azure database - SQLS with lots of restrictions -, or in Azure Tables. Azure Tables are a fast, non-relational lightweight service that typically stores entities and properties. Azure blobs are for arbitrary binary data - contents is whatever you put there.