Don't want to sound harsh and insinuate anything but did Zappos make any profit? I think the merits of 'Holacracy' that Zappos and Hsieh vehemently propagated can only be validated if it made any impact on the bottomline.
The reason I am saying this is because I worked in a startup which tried posturing like Zappos- flat hierarchy, no cabins, boozing, chilling et al, while being run by a cynic CEO. The startup failed badly so this cool culture never got the limelight but my hunch is that if they had raised enough money and survived another 5 years somebody would have included them in their book or dissertation.