That's just a packaging mistake then. What are these debian cowboys like? </joke>.
Contrary to what you've heard Akonadi doesn't require a configured mysql server running on the machine. It spawns a per-session instance of mysql running a custom config that is tweaked, minimal and secure. We started with mysql-embedded but after running into weird problems with it, went for the standalone process - it doesn't create significantly more overhead and we think we have the process management sorted.
You do still have to have an installed mysql though. Postgresql and sqlite support are being worked on, but we've run into a lot of problems with heavily multithreaded access to sqlite.