ItsAlwaysaPeopleProblem. So said GeraldWeinberg.
And supported by PeopleAreTheProblem, where most discussions on this wiki go.
Even if TheManagerIsTheProblem, ItsaPeopleProblem still.
The biggest challenge of SoftwareDevelopment is getting people working together as a team on things that add value. None of the technical challenges your project might face will be harder or more important than this. from ItsaPeopleBusiness
BusinessProcessReengineering appears to be resurging under different banners, previous failures been attributed to ItsaPeopleProblem by most of the founders; see, for example, the article titled "The fad that forgot people" at http://www.fastcompany.com/online/01/reengin.html.