In matrixed organizations, the functional departments (like Marketing and R&D) contribute staff to participate on products or projects, as needed:
(from http://www.vertex42.com)
The advantage is that employees still feel part of a functional group, can learn from their peers, and can move from project to project. The Product groups don't need to support all the functional groups and can use just the resources they require, when they are required. In practice, matrixed organizations can still be siloed, with the most attractive projects attracting the best people, and with hoarding of people and resources in anticipation of actual need. Employees may not know exactly to whom they report - the function or the product line - which can create a lot of stress if they are given conflicting instructions.
