It is hard to reach the entire team of a project. I know I can create a private discussion that is available to team members only but I'd like to be able to contact the entire team in the same way I can contact members individually (from their user page).

Yes.. I've got the same request.  

Does this feature request sound like what you want? http://codeplex.codeplex.com/workitem/25577

If so, you should add your vote to it.