This one does seem to be more informed (and I agree with a lot his criticism of MongoDB here), but it's almost like comparing apples to oranges. Things are done in MongoDB a certain way for a number of reasons (e.g., the query interface doesn't allow certain things in a distributed context that you could probably do with a SQL database). But I think anyone who's done large-scale MongoDB deployments can (or at least should) attest that it works well, but perhaps not as well as other solutions (or as well as it could/will work eventually/whatever).