Not particularly. If anything, it's a case study in how the older / more popular an online public community gets, the worse the average content quality gets.
Also, pretty sure there hasn't been forced anonymous in years.
The more I think about this stuff, the more I think there's almost a Smeed's Law[1] for communities, where the content quality is statistically dominated by the size of the community and not much else. But this would be next-to-impossible to formalize.
[1]http://en.wikipedia.org/wiki/Smeed%27s_law