It's as big as printing. Printing didn't significantly reduce oral communication, and hypertext won't seriously threaten printing. Subjects of later essays will be determined by then-current events. Then we'll discuss the types of hypertext and their corresponding tools. Now there's all that and non-linearity, too.
Linear communication goes in one sequence, determined by the author.
Linearity makes causality clear and verifiable, but it's a monologue with no audience input. If something is recorded , it can be preserved and distributed. And a record makes verification much easier, because you can refer to exactly what the author claimed previously. It's immediate, like oral and electronic communication. It's recorded, so it can be both verified and distributed.