Can't the members communicate through Private Messages(PM) each others? Why SE doesn't allow it?
This is not the goal of SE communities. It may change in the future, but I doubt. IMHO, PM is not going to happen anytime soon.
If you feel the need to contact a user, check his profile. Users that accept to be contacted usually leave their email address, blog of whatever. If the user don't put that information, it's a good indication that he doesn't want to be contacted.