I think I understand Jaron's premise - sites like facebook reduce the human element by forcing its users to add information according to a predefined structure. Presumably these same users may have created more free form web sites (and he equates this to individual creativity), but I don't really agree that it leads to group-think.

Facebook or any other site is just a medium - whether or not it leads to group-think is more a function of the participants than any conformity in their online 'meeting place'.