Regarding the on-going crisis of the nuclear plants in Japan, I received this (which I have abridged and reformatted as a numbered list):
So, what do we learn?
Don't use nuclear power.
If you do, don't build in an earthquake zone.
If you do, don't build on a tsunami-prone seaside.
Make sure the emergency cooling system works, even in an emergency.
Make sure the reactor is fail-safe in a power cut.
Of course, if you started with #5, #'s 1-4 would be superfluous.
I think the real lessons look more like this:
Don't be careless with nuclear power.
If you use nuclear power, don't stop your research and development efforts.
If you have to build in an earthquake zone, build to withstand all possible tremblors, landslides and tsunamis.
Make all your plants passively safe (if any are not, see #2).
Nuclear power has saved Japan an immense amount of money for imported fossil fuels, as well as the pollution from burning those fuels and dealing with e.g. ash. Even if several of these plants have to be scrapped, a small radiation release will not contaminate land (as Three Mile Island proved) and will not prevent rebuilding. Japan's nuclear balance sheet probably still shows a fat profit.
The biggest problem may not be the loss of the plants themselves (I understand that they are among the oldest in Japan), but the lack of ability to replace them quickly. The plants which make the large forgings for reactor pressure vessel heads are booked years in advance. If R&D had pushed forward over the last 40 years to yield e.g. small modular molten-salt reactors, it would be much quicker and cheaper to replace the lost plants. There might not even have been an issue, because the oldest, least-robust plants might have been replaced already. But that, sadly, isn't the world in which we find ourselves.