With well-defined structure, you can easily map the builds to certain parts of the source tree. In general, I am not a fan of this approach, as this model can be a mixed blessing. On the one hand, my check-in/check-out process can be simpler as I have only one repository to worry about. On the other hand, it becomes very easy to get into the habit of checking in source code for multiple services at once, which can make it equally easy to slip into making changes that couple services together. I would greatly prefer this approach, however, over having a single build for multiple services.
