"This is because you assume you'll run it on single server. MongoDB's documentation clearly, repeatedly, and earnestly tells people to run MongoDB on multiple servers."

Err, what?

I'm using MongoDB in production and I've looked at your documentation a bunch. After spending days with your docs open in a browser tab I can't say that it was especially clear on this point.

Perhaps I'm particularly ignorant, but I'd wager that not many other developers know that multiple MongoDB servers are currently required to achieve reasonably acceptable durability.