If thats really a problem host your database on a cloud platform and let those guys do the job of a DBA. Works for me at present. I am aware its not going to be a solution for everyone, though it still sounds a lot better than being your own Mongo DBA.

The DBA is the role who is reponsible for the organizations data. Even if you outsource the routine tasks such as "doing backups" you still need someone to assume that role.

Cloud service doesn't really replace DBA.

Yes, it will help you to cover cases like where the server phyically explodes, but that's basically irrelevant, most problems where you need a DBA are caused either by data corruption caused by application code or developer, or performance issues caused by DB structure - in those cases the cloud platform won't do anything for you, they just host the server. They can restore backups, do monitoring and tune the server, not your particular app/db structure - but all the big problems are there.

"most problems where you need a DBA are caused either by data corruption caused by application code or developer, or performance issues caused by DB structure"

Is running Mongo going to solve any of those problems? Without a rigidly enforced schema I would guess those problems are going to be amplified rather than solved.