When we chose MongoDB for a project, a dominant criterion was out of the box geo queries. It helped that the storage and query approach had good impedance match

When we chose MongoDB for a project, a dominant criterion was out of the box geo queries. It helped that the storage and query approach had good impedance match with NodeJS. From a query perspective, we wouldn't have benefited much from SQL anyway, since much of the reading is free text or social graph or location based search which we moved to Solr.