Stonebraker makes a point of saying that the lack of standards in NoSQL system prevents their adoption. While there are standards surrounding SQL most SQL databases do not adhere to the standards. They have connection semantics and syntax that are at times mutually exclusive. Drupal 7 has a dynamic query builder specifically to take care of this (see this podcast for more info http://www.lullabot.com/podcasts/drupal-voices-24-larry-garf...). But for most organizations, it's not like they can simply switch from one database system to another without a fair amount of work.
