It all comes down to people being severely misinformed and misled by supposed experts. You are probably referring to the fiasco with the open source Facebook co

It all comes down to people being severely misinformed and misled by supposed experts. You are probably referring to the fiasco with the open source Facebook competitor Diaspora and how they moved from MongoDB to MySQL because Mongo apparently wasn't up to the task. It's not the fault of any NoSQL database if someone makes the poor decision to solely rely on relatively new and untested databases like MongoDB or Couch. People are using the likes of MongoDB not because they've identified a technical need, but because it's cool and hip and people want to ride the hype train with everyone else. The hatred is more directed at the misuse of embedded documents as opposed to separate ones and people trying to make MongoDB work exactly like MySQL when it's completely different. Give it time and you'll see articles from people proclaiming it's the greatest thing to ever happen to databases and evident by the funding and money 10Gen have coming in, they must be doing something right.