SloFS (pronounced slow-FS) is a filesystem built entirely upon sqlite3. The purpose is to provide a single-file blob of data storage to applications that need it. Additionally, the second goal was to have a standard set of open tools with which to re-read the data back out with. As such, SloFS includes a set of commandline tools much like the existing POSIX ones (ls, mkdir, cat, rm, etc.) to make examining the data store easy.
Why not? During development of the pm password management tool, the authors found it necessary to have an open format, easy to read data file. Originally YAML was chosen for its terse and easy to write and debug data format -- unfortunately, the C libraries for parsing such a data structure are too painful. After considering other options, they finally came across zziplib. Realizing that their data format was just a simple set of strings and that reading and writing to a filesystem were simple and well-defined algorithms already, the authors set out to start using this library instead. Unfortunately, they realized that zziplib is a read only API to zip files, and finally came up with the crazy idea of implementing a complete filesystem on top of a very lightweight SQL database. SloFS was the result of their discussion and research.
SloFS -- It's not stupid, it's just slow.