Say the use scala to process incoming email etc.
In what context is (or could) they be running scala?
Can it run inside its own daemon?
Can it run inside of tomcat?
Or would you use it in a cron job?
or is it all of the above? :)
Sorry this is an open question, and I don't know much about scala, but I just want an idea of how one could utilize scala and under what context it can run in.
Scala is a general purpose language, and can be used pretty much everywhere that doesn't have restrictions of its own. One limitation it has is that it must be backed by a Java VM (or .Net if you go with the experimental stuff), which can bring limitations of its own.
When people said "backend", they usually mean using Scala to provide services to other software, leaving user-facing layers to other languages. This combination leverages the speed advantages of static typing in Scala, to benefits in the speed of development and interaction other languages -- PHP or Ruby, for example -- might provide for UI front ends.