There's a lot of existing document-oriented databases like RethinkDB such as MongoDB, CouchDB, RavenDB, ect and they all have the same network bandwidth problem for geo-replication http://acmsocc.github.io/2015/posters/socc15posters-final52....

I guess those other document-oriented dbms just had better early stage shilling to get funding before RethinkDB did, and by the time Rethink shopped around there was already enough competitors that investments in documented-oriented dbms dried up.

The current state of the art is an in-memory dbms to take advantage of future available (soon, 2017) non-volatile memory. CMU is developing such a dbms http://pelotondb.org/ and there's also MemSql and Sap Hana.