Pretty usefull article:
It’s only for propel though, interesting if similar approach would work for doctrine as well.
Here is the reason why Vidyut Luther had to use multiple databases:
I can’t just extend the existing application for reasons we don’t need to get into, but I do need to interface with the data, since the existing app doesn’t really have a nice way to handle a SOA, or share data easily, my next best option is to talk to the original app’s db.
But I guess the same will work for case if you need one backend and multiple databases (see our older article regarding it for symyfony 1.0.x: http://www.symfonylab.com/one-backend-many-sites/