@david.Poole

I reckon that it varies enormously with the product, and with a single product over time. In some cases, the data consistency problems haven't been exactly subtle. Did you see ...

http://blog.engineering.kiip.me/post/20988881092/a-year-with-mongodb

http://www.infoq.com/news/2011/11/MongoDB-Criticism

... but things have been quieter for a year so these problems seem to have been sorted out.