At my previous position with Code for America, I spent a bunch of time & effort walking our government technology fellows backwards from Mongo and Node, eventually banning their use altogether. I imagine that in the right situation these two technologies could be useful, but I’ve not encountered it yet. Mostly, the promises of quick setup and ease of use translated into sloppy DB design decisions papered over by external indices like ElasticSearch, and gnarled thickets of impenetrable pyramid code.
Sarah Mei and Eric Jiang explain further.
MEAN: not actually a stack, just a heap.