Re: mongo didn't eat anything
Mongo should only be used as a read only repository or a key-value scratchpad store
Or if you don't care about consistent and complete results - which is the case for many of the applications where NoSQL is used. If you're running some sort of social-networking site, for example, most end-user queries don't need to be consistent and complete. If some user searches your database of X piles of user-generated content for Y, they probably won't notice a few missing results; and if they think something is missing, they'll just retry the search with a slightly different query.
There are applications which don't need ACID guarantees because the users don't care.
Yes, NoSQL is not a replacement for RDBMSes - they're suited to different problem domains. But that doesn't mean there aren't applications NoSQL is suited for, beyond "read-only" and "scratchpad". (The value of those applications is a different, and more complicated, question.)