yeah, mongodb has flipped from hype to hatred without much in between.

The reason, I think, is that few people using it had a good sense of where the pain points would be. Many of us somehow imagined that because we didn't know where mongodb's limitations were, we wouldn't run into them. Cue frustration when you're bitten by some issue you didn't think about.

I do believe there are good uses for it. But they are pretty specialised, and I'd rather use a relational db for most things.