Digital is the new frontier, and the space is (virtually) infinite. I think the peak will be when advertisers compete against each other for your time, not your money. A person only has so much time.
We are at that point today, see the blogging around the "attention economy." Money is still the end game, luckily there is plenty of innovation happening around new ways to get you to spend more money without needing to apply any of your attention or wasting precious time.