I’m not sure it needs to be virtual – but that’s just me. I think it just needs to be the creation and exchange of content with communications or what many would call engagement. This has occurred in forums, emails, mobile phone texting, video sharing sites and image sharing sites.
There has been plenty of people try to create monolithic communities - some have thrived, like the public release of Facebook in 2006 and some have never left the launch pad. Not many social networks have lasted more than 6 years.