All three layers are important, it's how they're contextualized
This is something my company has spent a considerable amount of time on, both developing, and testing methods for increasing the abysmal adoption success rates of collaboration software (around 10%). We're releasing our adoption toolkit soon (it's in final sanity checks at moment), but you're welcome to an early preview here: http://www.sideraworks.com/preview-collaboration-technology-adoption-toolkit/
In regards to individual, group, and org segmentation I don't think you can separate the three in a successful adoption initiative. There are many interdependent sociological factors between those three segments.
Co-Founder and CEO, SideraWorks
Creating Social Business Success Stories