I seriously considered it for my organization a little over a year ago, and while ultimately it wasn't the right fit I think a clear document and explanation of how someone else would do it would have been very useful to think about.

I think part of the reason that they haven't succeeded is the necessary capital and scale of technology organizations these days. It seems there's a hollowing out of the mid-tier of bootstrapped organizations where a co-op would be feasible, and if you're a founder who is going to put in years of unpaid or low paid work and funding, giving up ownership is a tough sell.