"the two sources connected through a hyperlink have equal weight; neither one dominates the other. Thus the acceptance of hyperlinking in the 1980s can be correlated with contemporary culture's suspicion of all hierarchies..."
Manovitch implies that, since hyperlinks have an egalitarian relationship, they lend themselves to representing nonhierarchical structures. I think that this is a logical fallacy; just because an individual hyperlink cannot directly form part of a hierarchy, this does not imply that hyperlinks have a tendency to represent nonhierarchical structures. As a counterexample, I propose search engine rankings, which are reflections of the hierarchy of the world wide web.
Hyperlinks are one-way, which imbues them with a sense of directionality. I think that this does, in fact, constitute a relationship of domination. Although directionality does not immediately imply a hierarchy, it certainly lends itself to representing hierarchical structures, since a distinguishing feature of a hierarchy is that there is a sense of "up" or "down." The page near the destination end of a hyperlink could be considered to be nearer the "top" of the hierarchy, since its content has been judged by the hyperlink's creator to be of some value. A page which is on the destination end of many hyperlinks is higher up in the hierarchy of the web, since there are many pages "below" it that link to it. Search engines take this into account and place linked-to pages higher up in their rankings, which reinforces and lends a stability to the hierarchy of the web. These linked-to pages are at higher levels in the hierarchy, not only because other web pages link to them, but also because search engines, which currently form the top of the web hierarchy, have given them the validation of a good ranking.