[mrkurt]

Eventually consistant replication is not unique to MongoDB, most DBs have an async replication option. Using "not Mongo" won't really solve it.

[krichman]

An option is not a default, though, so using Postgres or MySQL absolutely would solve the problem of returning with success before persisting the data.

The contentious area isn't really that Mongo does this, it's because for whatever reason the people trying it don't expect Mongo to do this.