I didn't say Eventual Consistency. I said Occasional Consistency. MongoDB is has hard Occasional Consistency. Indeed, it is the most occasionally consistent database I know of. I once wrote a few million records into Mongo. It was consistent before the write, but never again after.

Great for sub-linear time algorithms! At that point, all my algorithms ran at less than O(n) on the size of the data I had written in.

From a business perspective, Occasional Consistency is also a very nice property if you are storing audit data for certain types of organizations. It gives complete plausible deniability about rule compliance.