That's seriously debatable. For one, there's already a lot of clutter without viral marketing but I think the universe is starting to work out that plenty of people are not, in fact, total idiots, and most know about Google. But viral marketing is the future of advertising because it pays for itself. It provides context that enthuses consumers, it's dirt cheap, and it complements boring advertisements. The fact is that trailers before the movies don't matter if no one sees the movies anymore, and the 30-second TV spot doesn't matter if no one watches the commercials anymore. Viral marketing has of late actually begun to become commonplace and I don't doubt that in a couple years it will be a staple. You can't ignore the fact that old marketing techniques aren't working and that there is an ENTIRE platform that has been ignored for far too long in 2008. The internet has changed user demands. People want to be able to to interact with things, in the same sense that you'd test drive a car, before they buy your product.
Advertising as we knew it is dead. Viral marketing has upped the ante. It is necessary to use the internet to market a thing today.