Galleycat posted a great infographic on 40 years of ebook publishing here.
The points I found most revealing are:
The first ebook was launched in 1971 by Project Gutenberg. This points to the importance ebooks held before most traditional houses really understood their potential.
In 2000, Stephen King’s novella Riding the Bullet was downloaded over 400,000 times in 24 hours, proving the ability of ebooks to reach existing fans and new readers.
Amazon launched Kindle in 2007, five years after traditional publishers began working with ebooks. So Amazon is not always at the forefront of publishing trends.