[Air-L] Social network site nomenclature

All, Much of the available research refers to services such as Facebook and MySpace as "social network(ing) sites/services (SNS)." Let's ignore for the moment the differences between those four permutations as I'm more interested in learning about why some researchers use "online social networks (ONS)." SNS seems to be much more common, particularly in the wake of the late 2007 JCMC special theme issue focusing on SNSs. Given that both terms are still in use, is there some sort of subtle cultural or discipline-based divide of which I am unaware? Or is this just an oddity that isn't important or indicative of anything more than personal preference? Kevin