The primitive need to exchange experiences, to a species that survived for millennia collectively, is reflected either these days in the User Groups (UG).
From Neanderthal campfires (exchanging experiences on hunting or gathering fruit) to the current learning experiences, what changes is the tool. The process of construction of meaning is the same.
Six or seven thousand years ago our ancestors left evidence, in petroglyphs and in primitive tools of communities of hunter-gatherers, of our natural predisposition to social cooperation. We learned that the survival of the community depended on sharing knowledge. We lost this surviving feature in hostile environments when we started to dominate the agriculture and livestock: we built villages that limited our mobility, we created rules, social institutions, cities, armies and companies. From a collaborative species we become individualistic beings. 
Now, through the UG we are learning again to work collaboratively, both in physical as well as in virtual spaces.
The impact of social networks on UG is incontestable. Nowadays virtually the entire social life of the community migrated from the Discussion Lists (DL) to Twitter, Facebook, among others.
I have observed in the DL of my group, and other Java User Groups (JUG), every day the contents has become almost exclusively technical (pure Bits & Bytes). Our DL have become a space for the exchange of pure technical knowledge, more focused on … How to do it?, … Show me … and, on the other hand, it seems that the community social life (job offer, developer behaviour, gossips, news) has migrated to Social Networks.
The UG has to be where its members are, and the solution is obvious: today the group have to be on social networks. But, where the users are located?
In a recent article, Poyan Sandnell asked “Did you know: Facebook is the third-largest country in the world?” 
The answer surprises and shows the tendency, it seems to me, that UG are following (or will fade away):
5: United States
With 1.23 billion users around the world the probability that your UG members are Facebook’s members too is not negligible. 
Choosing a platform with which one has more affinity tends to shape the perception of the world, from the perspective of the community that uses this service. 
Technology flame wars happen all the time between groups, people defending this or that platform only because someone invested more time learning how to use this or that tool. We love what was hard to conquer.
Twitter or Facebook? Twitter is more like Wikipedia than, say, Facebook. Twitter is not so much about connecting with your friends, it’s about broadcasting information.  Is more one to many, and Facebook on the other hand is more many to many.
But, what about Twitter as an social environment for an UG?
I choose Twitter for my field research because I need a very fast, easy tool for broadcasting my weekly questionnaire to the volunteers developers. A tool that everybody could have, in any cheap mobile (cell phone), anywhere in the world.
According to research, conducted on a random sample of about 300,000 Twitter users in 2009, 25% of Twitter users don’t tweet at all.  They only read what other posts, they lurk. In the same direction a report from the Harvard Business Review showed that the majority of Twitter users are passive and only 10% of participants are responsible for 90% for all content produced. 
According to my own research 82% of JUG members are Lurkers (they don’t participate) and only 12% are active members. What we need for the social activities of the community is a DL for all, a space where people feel free and safe to interact.
Don’t take me wrong here, as a form of membership, the Lurkers are very important element on the UG ecosystem. They are not free-riders, a heavy burden to the community as the leaders usually think (at least I did a lot!). They are the large, silent majority of users. 
They don’t participate because they feel uncomfortable about posting their thoughts, after reading some of the uglier flames, the tone and hostility of public forums. Here Julia gives her testimony: “I am afraid to post because the incredible arrogance and hostility among some people on sites like this.” “I’d like to learn Linux, but I don’t get the feeling that these people would help me. They would just make me feel stupid.”  Mason said: “people who lurk do so because they do not fell competent to post.”  I believe that Lurkers don’t participate because they are self protecting.
My hypothesis is that the Lurker in one community could be an active member in another. This action of lurking in your community is because the participant is in search of innovation, to take it back to where s/he is an active member. They can be the bridge that pollinates the innovation (bringing new knowledge) between communities.
On the other hand, flamers, trolls, bots, spammers, porn freaks, griefers and other troublemakers are vital to communities too. They have a social role in the DL, because they leverage the community benchmark. In creating problems they force people to think, be indignant, react, and eventually… learn.
So, in my opinion, if the goal of your group is to “help people”, change their lives one line at a time, create for your members an amazing and friendly experience for knowledge sharing, (a) the community need to keep a private space to exchange Bits & Bytes …
– It’s not good expose the trial and error learning experiences of the developers publicly, where external people (like Headhunters and other possible contractors), can get a bad idea of what is happening.
– Experiential learning is key to meaningful learning 
– Error is an option! Actually it is a fundamental behaviour in learning. 
– Eventually could be a private space, accessed only by subscription, inside in one of this open SN.
… but, (b) the social life of the UG should be on an open and transparent social networks.
Daniel – Dr. JUG
JUG Leader / Founding Java Champion
I thank Sebastian Dziallas for helpful support.
1 – TAPSCOTT, Don. Wikinomics: como a colaboração em massa pode mudar o seu negócio (How mass collaboration changes everything). Rio de Janeiro: Editora Nova Fronteira, 2007.
2 – SANDNELL, Poyan. Did you know: Facebook is the third-largest country in the world? Available at: http://www.ericsson.com/thinkingahead/the-networked-society-blog/2014/07/14/know-facebook-third-largest-country-world/, accessed: 2014-12-05.
3 – Facebook’s 10th birthday: from college dorm to 1.23 billion users. Available at: http://www.theguardian.com/technology/2014/feb/04/facebook-10-years-mark-zuckerberg, accessed: 2014-12-05.
4 – SPYER, Juliano. Tudo o que você precisa saber sobre Twitter (All you need to know about Twitter). São Paulo: Talk2, 2009. Available at: http://www.talk2.com.br/conteudos-exclusivos/, accessed: 2014-12-05.
5 – SCHROEDER, Stan. Twitter is Not Your Average Social Network. Available at: http://mashable.com/2009/06/02/twitter-users-dont-tweet/, accessed: 2014-12-05.
6 – HEIL, Bill; PISKORSKI, Mikolaj. New Twitter Research: Men Follow Men Available at: https://hbr.org/2009/06/new-twitter-research-men-follo, accessed: 2014-12-05.
7 – Nonnecke, B. and Preece, J. (2001). Why lurkers lurk. In Americas
Conference on Information Systems, pp. 1-10.
8 – Katz, J. (1998). Luring the lurkers. Available at: http://slashdot.org/features/98/12/28/1745252.shtml, accessed: 2014-12-05.
9 – Conner, M. (2000). Linking, Lurking, Listening, and Learning: An interview with John Seely Brown. Available at: http://www.johnseelybrown.com/linklearn_int.html, accessed: 2014-12-05.
10 – PERKINSON, Henry J. Learning from our mistakes: A reinterpretation of twentieth-century educational theory. Westport, CT: Greenwood Press, 1984.