The Internet existed before the World Wide Web, but until Tim Berners-Lee's proposal most systems organised information hierarchically. The invention of the hyperlink is at the core of the web, and what makes it a true interconnection of knowledge rather than just a bunch of servers.
The inventor of the web, Sir Tim B. L., went on to propose the Semantic Web, which introduced new types of markup that programers could use to make the web machine readable. However, it was too complicated:
And so the “Semantic Web Activity” at the Worldwide Web Consortium (W3C) has spent its time writing standard upon standard: the Extensible Markup Language (XML), the Resource Description Framework (RDF), the Web Ontology Language (OWL), tools for Gleaning Resource Descriptions from Dialects of Languages (GRDDL), the Simple Protocol And RDF Query Language (SPARQL) (as created by the RDF Data Access Working Group (DAWG)). Few have received any widespread use and those that have (XML) are uniformly scourges on the planet,— Aaron Swartz's A Programmable Web: An Unfinished Work
Meanwhile, the hashtag was proposed on Twitter, and it was simple enough that it took off. Hashtags make it easier to for people to find the stuff they are interested in, and for computers to understand what kinds of things people are talking about.
What if... we could could use hashtags to help A.I. understand what we mean, without having to write all that semantic web gobbledygook that Sir Tim B. L. and the W3C thought was necessary?