MongoDB is evil. It…

… loses data
… in fact, for a long time, ignored errors by default and assumed every single write succeeded no matter what (which on 32-bits systems led to losing all data silently after some 3GB, due to MongoDB limitations)
… is slow, even at its advertised usecases, and claims to the contrary are completely lacking evidence
… forces the poor habit of implicit schemas in nearly all usecases
… has locking issues
… has an atrociously poor response time to security issues – it took them two years to patch an insecure default configuration that would expose all of your data to anybody who asked, without authentication
… is not ACID-compliant
… is a nightmare to scale and maintain
… isn’t even exclusive in its offering of JSON-based storage; PostgreSQL does it too, and other (better) document stores like CouchDB have been around for a long time

Please read the full article with source on every statement on: http://cryto.net/~joepie91/blog/2015/07/19/why-you-should-never-ever-ever-use-mongodb/