hack3r_n3ws

I don't think you understand what is being discussed. ACID compliance has nothing to do with "security". It's a matter of transactional guarantees. MongoDB offers none because it is not ACID compliant. That means that transactions can silently fail, partially commit, execute out of order, etc. This is an EXTREMELY serious and complicated issue. And I would not do any banking, trading, etc on a non-compliant database.

And if you build ACID on top of mongodb, then you lose the benefits of NoSQL. Not to mention the immense difficulty of building ACID into your business logic...

It makes sense to use mongodb for commenting system where nobody cares if you lose a comment or certain comments are written before others.

But no competent architect would use mongodb for financial/currency transactions.

If coinbase did use mongodb, it will be inevitable they will have transactional issues. The more popular coinbase gets, the more transactions they process, the more issues they'll have. I don't envy the poor souls that have to track down these kinds of issues...