>Really? Hmm..The only place I can see where I might use something like this is during development. Having the users change the data source on a regular basis gives me the willies. I can just imagine how many times they'd apply changes to the wrong database. Ugh...

It is critical for my application.

Imagine a billing service doing work for several different healthcare providers. When the employee logs in, a list of databases that can be used by that user is displayed. The user selects one and works there. After finishing, that user needs to select a different database. This process continues throughout the day. The customers absolutely do not want any data co-mingled with any other customers.

Another similar need: Our company has an outside accountant that does some work for us weekly. The accountant brings in his laptop and works at our place on our data (on his computer). He gets information from forms that we do not removed from our premises. He has all his other customers on the same laptop. He uses the same program for all of them.

I think the need to have many different databases (same design but different data) for the same program is a very common need. Intuit's Quickbooks has this feature.