[silentbicycle]

Monotone (http://www.monotone.ca/ : a DVCS that predates git by several years, and was a major inspiration) keeps its repositories in SQLite databases, as well. I used it for a while, kept my home directory in mtn, etc. SQLite databases are indeed quite easy to back up. (You're better off putting "echo .dump | sqlite3 dbfile.sql > dbfile.sql.bak" in cron, though - the dump is more portable.)

Using SQLite dbs for serialization is a great idea, particularly for prototyping. It's not quite as efficient as bespoke file formats and data structures, but frequently good enough, and getting transactions for free is a huge bonus.