Interesting to read both the article and comments. It's cool to hate Mongo nowadays but we use it successfully (for PEPS, open source: https://github.com/MLstate/PEPS).
The version of MongoDb used is not mentioned in the article. The changes between versions is a problem with Mongo but it improved much recently.
One problem clearly identified is the lack of model. There are solutions to this. For instance, with Opa (http://opalang.org) we use strong static typing to generate a database model and guarantee that the whole applications sticks to it. That leaves out model changes, but there are solutions for that.
Also, there is no need to have the whole collections in RAM, but clearly enough RAM for the "working set" helps.
In the end, Mongo is no magic so do SQL databases which have their share of problems too.
The version of MongoDb used is not mentioned in the article. The changes between versions is a problem with Mongo but it improved much recently.
One problem clearly identified is the lack of model. There are solutions to this. For instance, with Opa (http://opalang.org) we use strong static typing to generate a database model and guarantee that the whole applications sticks to it. That leaves out model changes, but there are solutions for that.
Also, there is no need to have the whole collections in RAM, but clearly enough RAM for the "working set" helps.
In the end, Mongo is no magic so do SQL databases which have their share of problems too.