My friend Niclas got me to do some welcomed thinking in a thread all but a moment ago. And I might as well take the opportunity to make it the first post in my very new 'Reflection' category on this here intermnetpage site.
Here goes:

Let me suggest the following definitions:
A tribe is a group of people that are dependent on each other for survival and who shares resources for their basic needs, whereas a community is a group that to some degree interact in their social life.

The structure of tribes of the old I would guess to be rare state in the modern world (although exceptions exist, check out S. Jungers - Tribe), but in those cases they do exist they seem to have a deep impact on its participants, and in a genetic sense we could very well be wired for such instances (again check out Junger).
I'd say we're involved in several communities throughout our lives, though the foundation for a community can be very shallow, let's sat they can range from the hobby group to your family.

So if we see a spectra of social interdependency, ranging from your the curling club to an amazon warrior tribe, it becomes visible that there is a scale of sorts. (This seems to be my first point, let's call it the point of socially interdependent scaleability)

From what I've been reading and experiencing lately, one issue with modern society is the fragmentation of our communal life - we do not depend on the same persons in all aspects of our living (work, social activities, hardships etc) and this I believe affects our ability to create deep meaningful bonds. Rather than having several individuals that you share your person with, we spend our time in different areas, playing different roles with other roleplayers. (This, my second point, could be called 'the fragmentation of communal effort', 'modernizised areal roleplaying syndrome' or 'Steve Ray')

I've at times stopped and realized that I do not know the professional side of my friends, nor the personal side of my work colleagues. Neither have I been able to share the respective sides of myself. That is, I have not fully come to know the complexity of the individual or shared the complexity of me. In those instances where I have gotten that opportunity, I've also created some of the stronger connections.

The tribes of old I believe are gone, and maybe for the best since the word tribalism not for naught have some dark connotations to it. I do however see that there are needs in us that more deeply reach satisfaction within a community that to a greater extent incorporate you as an individual rather than as a function for a specific area in life.