Ideally, all members of a project should be communicating with each other and the project manager. If that were not so, there would be no way for the PM to know what was getting done, or for different members to learn about the progress of the project, avoid pitfalls, etc. In the company that I work with, Skype IM’s, Skype meetings, emails, and face to face communication are the main ways that people communicate within a team, and I find these avenues cover all the bases of communication: Skype IM’s help with quick questions and mini status updates, Skype meetings provide a place to give more comprehensive updates/allow team members to talk and ask questions to the PM and each other, and emails help in formal communication that must be documented. In person talks tend to serve the purpose of most of the mentioned depending on the proximity of team members (some team members may be in another country so this may be unlikely to impossible). Overall, the most important thing in defining communication channels is that everyone agrees and that the most effective and appropriate means are used. If you know someone never responds to IM’s or emails, if they are in the building, perhaps going to them in person would help. Or if someone is offline, IM won’t work so email is the way to go. Selecting the best method of agreed upon communication for the situation is key to facilitating information flow.