I would not say prevalence, because it implies an alternative which is not prevalent. The is no other Internet over which to prevail. "Ubiquity" is the word you're looking for.
www.dictionary.com:
u·biq·ui·ty ( P ) Pronunciation Key (y-bkw-t)
n.
Existence or apparent existence everywhere at the same time; omnipresence: “the repetitiveness, the selfsameness, and the ubiquity of modern mass culture” (Theodor Adorno).