Answer: The "Fundamental Shift in Power" means, the shift from the established media outlets such as publishers, television, radio, newspapers, and major distribution.
Explanation: Before Social Media, you had a better chance of winning the lottery than getting a legitimate publisher, publishing your book. Now, you can self publish, for free, and have it distributed worldwide for free on Amazon along with their other 3.5m books. If you want your own radio talk show, just get a free account with BlogTalkRadio. No longer do you have to pitch Clear Channel your topic, prove you have a 100k listener base and give them a check for $250,000. It's free.
All of the previously difficult and expensive forms of communications and distribution channels are now available to everyone for free. I call it the "democratization of technology".
With that comes the downside. When any idiot can publish a book, every idiot does. When any fool can have their own radio show, every fool does. Without the barriers entry, there are now quality standards in place.
The result is, the Internet, Amazon, blogs, On-Line Radio podcasts, etc. are filled to the brink, with trash, and useless, opinionated, unverified, biased garbage. While it gave a voice to so many who deserved it, it destroyed the value of nearly all available content. This has resulted in the really good and worthy content being buried in a pile of trash, never to be found.
Lon Safko, the author of The Social Media Bible