The design of distributed systems for collaborative work or learning requires that both humans and machines be organized such that the potential and limitations of the human-machine interdependence is optimized. Current distributed architectures like peer-to-peer and Grids have not yet been optimized to support the needs of collaborative applications. In this paper, we investigate the requirements of collaborative applications for groups and, discuss current Grid and P2P architectures with regards to this. need. We suggest possible extensions described in a "function dispersion architecture". Finally, we present as case study our recent work on the design of a middleware to provide services for distributed collaborative applications that has been validated by simulation and prototyping.