- Performance: in some cases, complex queries are not required (or can be replaced by simple ones): databases that perform very fast with pure primary key retrieval
- Complex datastructures are not needed
- ACID is not needed, i.e. mostly simpel writes are performed but fast reads necessary
- Agile development seems to favor rather ad-hoc data-structures vs. carefully planned ones (if this is a good trend is written on a different page)
- Distribution is important and distributed relational databases are a hard thing to do
- Access to rather document-oriented datastructures is required
Btw.: does anyone know other projects in that domain that I have not seen yet?