Many times a revolution is initiated through the introduction of a new way to do something or a new product. A revolution isn't justified until people can't imagine life without that element or product. That's when a revolution becomes a true success.
The great thing about revolutions is that they change people: culturally, socially, and even economically. And in this case, the digital revolution changed us all. It made us digital consumers.
In terms of driving digital consumerism, e-mail has been at the forefront. It allowed for mass, personalized marketing delivered as a digital version of analog direct mail. E-mail fulfilled the transactional communication needs when selling without meeting face-to-face in a brick-and-mortar store. And, e-mail wasn't competing with other online communication channels.
E-mail became a strategy. So much so that an entire industry built up around using email as a marketing tool.
Where I see the change with the rise of the social web, is that the strategy is changing to "Communicate with customers in the digital channels they use" and e-mail is shifting to a tactic within the larger group. Because most online communications channels are still relatively new, the fare of early adopters, the e-mail channel is still king.
And I do expect that it will remain the king for a while. But as other technologies reach their tipping points and gain mainstream adoption, I also expect that e-mail will target a more narrowly defined segment rather than the general population it is assumed to reach now.