[old-gregg]

Do your research. "document-based" DBs already "ruled the world" right until relational databases were invented, which quickly obsoleted them.

The only advantage of disk-backed hash table is ease of scalability, this is why they're useful for hm.... top 0.005% of web sites, who handle thousands of updates per second.

[jshen]

They are also useful for rapid app development or prototyping. I've used couchdb this way a few times and it works great.