Where does development mode end and production mode begin? With the Software as a Service model you can release updates to your code on a biweekly basis. That m

Where does development mode end and production mode begin? With the Software as a Service model you can release updates to your code on a biweekly basis. That means the code (and potentially the schema) is always changing. While it is certainly possible to be clever and do things by hand this gets difficult to manage when you have a team of developers and multiple development, testing, staging and production environments. At my current job we use an internal tool that does some of the job but most of the time I want to fallback on using plain files for some data storage because subversion will version and merge it appropriately. I was more curious about whether or not others out there are using better solutions.