As the original article said, I think where MongoDB shines is as a glorified, souped up cacheing tier, competing directly with Redis, Couchbase, and similar. It's not really a good general purpose DB.

> I'd like to get a picture about why Mongo seems to be used more often than Couch.

Very good marketing from 10gen on the one hand. On the other, CouchDB is older (and we techies love the new hotness), and the CouchDB/Couchbase split confused a lot of people. Having your original founder found a different and incompatible project with almost the same name but very different goals would cause almost any project to stutter.