I think a successful social network is where there are millions of members, applications, groups.. much like Facebook. So my question is why would you want to create your own (like have a social network module on DNN) when the major ones are free and yours would never come close to what the big guys offer.

What would you get from your own that Facebook doesn't offer? Beside limiting membership.

I read today about the developer of Smart Thinker offering the whole module for free including source sighting the lack of revenue from selling DNN modules and giving up. I hope this is not an indicator for DNN modules in general.

This seems sad. I haven't used Smart Thinker but it contains several modules and I am sure a lot of development went into it but my guess is that sites like Facebook killed the idea. He mentioned he started working on it before Facebook came out.

Coincidently my post seems to be related to the fact maybe there's little demand for creating custom social networks but maybe not. Sites like Ning seem to be hosting thousands of these social networks and doing fine.

However I am saying that a social network is a pretty complicated site and major undertaking and I wonder if targetting DNN audiience only is an economically viable option.

Another reason for an own Social Network: Implementing a corporate intranet as a Social Network. Contents are usually not for the public so you cannot/should not use a public Social Network. You also don't want or need the users of a public Social Network but only your employees.

I think Wikis were the start for Social Media/Web 2.0 in the corporate world. Even Blogs are nowadays utilized for corporate purpose. Other Social Media/Web 2.0 follow or will. So a Social Network which is integrating everything into one system will replace the old-fashioned, top-down and uni-directional intranet world. Instead, using a Social Network can encourage employees to participate, generate and share knowledge, strengthen the employee community and corporate culture and simply be state-of-the-art instead of communicating the Web 1.0 way.