Before the printing press was invented, culture was mostly transmitted by speaking to people. Not many people had the skill to speak well, but enough of them did and so we had stories, epics, sagas, songs, and poems spreading from mouth to mouth. Books were limited to a few people at first, and therefore they did not really change the big picture. Interestingly, the few books that did spread were copied by hand, and were somewhat read-write; scribes could make changes to the text as they saw fit, and sometimes margin notes entered the main texts. The printing-press, however, changed everything.
Suddenly everybody could buy books and newspapers. At the same time, the people whose words did not appear in print were heard less and less. When radio spread, the same thing happened. Those who had access to the stations were heard. The others were not. This time, listening required but a tiny investment: A little money to get a radio, and a little concentration to listen to the program. Television changed the kind of messages that were spread. The culture was changed by the visual broadcasting medium. It required a little more money to buy a television, but the messages were all the more captivating. But one thing remained the same: Those who had access to the stations were seen and heard. The others were not.
The web promised to be different. It had GET and PUT – read and write. But the first web-server implementations didn't implement PUT. And so the web was modeled after existing broadcasting media: If you had access to a server, you were read. The others were not. Getting access to a server was certainly easier than getting access to a radio or television station. But it could have been even easier.
Blogs and Wikis have changed this a bit. The Web can be both read and write again.
Publishing on the web is a requirement if you want to "learn how communicate in the language of the twenty-first century." Blogs and wikis allow you to do that.