I'm curious why you would say this. I understand that most of the people here are coders and github or the like would be a good place to point to potential employers for work samples, but a "1990s style mailing list" isn't going to increase your visibility enough to get hired. It almost sounds like you think a presence on the internet at all is a good end in itself.
> Politics always talks about the gap between rich and poor that gets bigger and bigger. But the same is true for the gap between people who take part in the internet and use it to their advantage, and those who ignore it. Both these gaps already overlap to some degree, and that overlap will continue to grow!
I agree in part, but there is a third category that the OP hints at which is "consumers of information who don't create". Most people use Facebook, Twitter, etc. for consuming entertainment and advertising their identities, but they are not using it for any advantage. People may be able to use them to network, but most don't, and there is nothing inherently worthwhile in using social media by itself.