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GitHub User: tdm00
Excellent, thank you for that.
One think I learned, from watching a nodejs presentation actually (http://tv.adobe.com/watch/max-2011-develop/nodejs-and-you/) is that nginx is non-blocking whereas Apache is. The presenter covers this with a slide and illustration pretty early on, but nginx accepts the browser request, hands it to unicorn, then takes the next one whereas (he explains) Apache waits until the request is finished.
I ran into this same problem. Turns out that Ubuntu is deprecating the "admin" group in favor of the "sudo" group, as that's more consistent with the upstream implementation and Debian.
I found this is the Precise release notes at https://wiki.ubuntu.com/PrecisePangolin/ReleaseNotes/UbuntuDesktop