Foundation Series

I just finished the Foundation series by Isaac Asimov. Its a 3 book science fiction series taking place far off in the future. This was my first time really reading science fiction and my first time reading Isaac Asimov books (I was lured into the series after reading his short stories The Question and The Last Answer).

Without going into too many details, the series takes place at a time when :
1. There are quadrillions of human beings
2. Humans live across the universe on multiple planets and in multiple galixies
3. Inter galaxy space travel is fast and cheap
4. Nuclear fusion is widespread and very small ( smaller than iPhone)

Overall, the series was a great read. It touches on the rise and fall of civilizations and empires over time and has awesome technology (think personal body-armor shields powered by your own nuclear power plant). I'm surprised Hollywood hasn't turned it into a trilogy yet (think Star Wars, Lord of the Rings).

One concept from the series that stuck with me is the potential for a loss of societal-knowledge over time. I initially thought that humanity continually improves upon the foundation of the past (at least from a scientific / technical perspective -- certainly not always from a social perspective). This idea is well conveyed in the popular Newton quote -- "If I have seen further it is by standing on the shoulders of giants."

In the Foundation series, the "shoulders of giants" tend to disappear rather frequently. For example, worlds regress from nuclear power to coal / oil power as their society either lost ( through war) or forgot (through laziness of future generations) the base knowledge needed to even maintain existing technology.

When has this occurred on earth? One instance I can think of is languages disappearing as future generation stop using them. Another is knowledge lost in a Lighthouse of Alexandria type situation. Any better examples (especially of technical de-advancement)?

Even more, what can be done to avoid this outcome? Putting moe knowledge on the internet (until something causes all of our hard-drives to go dead)? Having humans on multiple planets (especially for the humanity-ending meteor type losses of knowledge)? Making giant vaults of seeds?

Or is it just a theoretical problem that we'll only regret not focusing on after the fact? I'm betting that I won't be around long enough to find out.