I’ve come across two Africans on the interweb. One was from South Africa as well. As for the other one, I only stumbled upon a single anonymous post of his/hers, defending the continent in a thread complaining about it. (Pointing out that there are places in Africa where people have high enough living standards to have access to the internet.)
Technology aside, I suppose another thing that might keep certain parts of the world separated from you and me despite the interwebs, would be language. Nowadays many people all over the world work hard to learn English, but I can imagine there are also still places where nobody bothers to. For all I know there might be entire Swahili-speaking, Indonesian-speaking, Azerbaijani-speaking, Nepalese-speaking and Arabic-speaking communities on the internet that we never touch upon.
From what my Chinese classmate tells me, I get the impression that the Chinese-speaking internet is quite extensive. I’ve also been a member of some exclusively Dutch- and French-speaking web communities myself.