Private and business communication and collaboration is increasingly being freed from temporal and spatial constraints. Many traditional ways of interacting which required temporal or spatial coordination have given way to much more flexible and adaptive distributed and mobile interaction styles among businesses and people. The research questions arising from such environments were the subject of the Forth IEEE International Workshop on Distributed and Mobile Collaboration (DMC2006) at WETICE 2006, summarized in the following. The workshop featured 8 full papers (out of 15 submitted) on topics ranging from emergency system architectures to collaboration and coordination support to co-presence in social networks. The discussions at the workshop brought up important issues and interesting research questions in various research areas touched by distributed and mobile collaboration.