Pervasiveness of Virtual Directories?

Does anyone know what the actual market penetration of virtual directories is? How many mid to large sized organizations actually use a virtual directory in their infrastructure? With all the debate on virtual directory vs. metadirectory recently in the blogosphere, one of Nishant's comments caught me off guard, when he was responding to Matt's statement that there "...has been a ground swell of apps that directly support Active Directory as the user store":

"And how are more applications supporting AD anyway? A lot of that has to do with the emergence of Virtual Directory solutions. A number of applications in the Oracle stable today claim to support AD as the identity store. The mechanism for all these is moving to Virtual Directory NOT because Oracle has a Virtual Directory product, but because maintaining adapters/connectors/plugins and what have you for all LDAP variants is a colossal nightmare."

Woah...that is a a huge claim there. Is it possible that the "groundwell of apps that directory support Active Directory" is due to "emergence of Virtual Directory solutions"?
Although I usually find what Nishant has to say as thought provoking, and the fact that every organization should be running a virtual directory solution is pretty evident by now, that claim sounds pretty absurd to me. What are the actual market numbers of the virtual directory solutions in production? (I know Radicati had some numbers around this, although I haven't gotten my hands on the paper yet.) Now compare that to the number of companies running AD. Even without the numbers, I think that Nishant is way off here. App support for AD is due to its undeniable pervasiveness, not because of the emergence of virtual directory technology.

Jeff Bohren has some interesting comments on the same post. Check it out.