in the last couple of month reading this site, I see more negative MongoDB reviews than most other 'cool tech' stuff. On one hand MongoDB by carrot-or-stick was pushed into environments with high-write needs (OLTP kind of systems). On another hand having true secondary indexes and semistructured data makes Mongo a 'closest to RDBMS' choice. So things like global write lock, indexes must fit into memory, auto-sharding questions, single-thread map-reduce -- all are pretty significant limitations for an OLTP data store. I wish MongoDB does not get discouraged and instead steps back, reviews academic foundations of the system and pick a couple of use cases and optimise their builds for them (similar to datawarehouse vs oltp kind of offerings)