It shows the power of marketing and ideology (people like mongoDB because it's fast on a single node and they can use SQL rather than having to learn something new, so they become "believers" in it without regard for its lack of scalability, or reliability, etc.)
It's a data model that works very very well for some datasets. We use MySQL for stuff that is obviously relational, but we store a bunch of geo data as JSON for fast serving to javascript etc. It's a perfect fit.
But seriously, if you don't have a backup of any of your data stores, that's a big problem.
To be little more serious, this is an example of what happens when professional sales strategies from proprietary shops come to open source. Now we have open source crapware.
Actually, the best heuristic to evaluate open source project - why it was created - for sale, or for internal use. Ryak or redis, for example, were made for use, not for sale.
You can use SQL on MongoDB? And thanks for telling people who like MongoDB why exactly they like it.