The general idea behind Amdahl's law is that improving one thing may cause other things to be the limiting factor. The discovery that we could prevent scurvy just by getting enough vitamin C was great, and it all-but-eliminated scurvy-related problems from our lives, but it doesn't do much for other problems, like hurricanes, alcoholism, and monkey gangs. I personally would love to have a magic bullet that would prevent me from ever stubbing my toe. It wouldn't solve all our problems, but I have yet to find anybody, even masochists who get off on severe pain, who wants to continue getting stubbed toes. Amdahl's law isn't something you can get away from, but it's something you can work with.
Gustafson's law, which you linked to, isn't a rebuttal to Amdahl's law -- more like an addendum. If you have a really good solution to one problem, you can sometimes recast other problems in terms of it. If we ever get our shit together and start churning out Liquid Fluoride Thorium Reactors (PDF) in bulk, then it would do more than solve our electricity woes. We could take some other problems -- not enough fertilizer, shortages of fresh water, oil supply problems -- and recast those in a form that we can solve with LFTRs. The high temperatures from LFTRs can make ammonia, synthetic fuels for internal combustion engines, and fresh water. One solution becomes many solutions.
People have very strongly biased view against existence of magic bullets - most of the worst problem we historically had had been solved with a magic bullet. However - because the magic bullet solved them so well, the problems don't seem to have ever been that bad from today's perspective, and therefore magic bullets seem much less significant than they were.
An average person in let's say Medieval Europe's had biggest problem like:
There's considerable amount of evidence that willpower is severely diminished if blood glucose get down, and this effect is not limited to humans. And a small sugary drink at the right time is enough to restore it.
We're talking really small numbers. Total blood glucose of a healthy adult is about 5g and it varies within fairly limited range. Then there's maybe 45g in total body waters. Then there's about 100g of glycogen in liver, plus yet larger amount in muscles and other organs, but which doesn't seem to take part in sugar level regulation. For comparison a small can of coke contains 33g - a really small amounts at appropriate times can make a big difference.
This leads to two issues. First, is blood glucose a good explanation for willpower deficiency and therefore akrasia? I'd say there's significant amount of evidence that some effect exists, but is it really the most important factor? Humans are complicated, science knows very little about how we work, and probably half of what it "knows" is false or at best only half-true. Caution is definitely warranted.
And the second issue - if this theory was true - and by manipulating blood glucose levels you could achieve far greater willpower whenever you wanted, what would you do? It seems that exploiting it isn't that easy, and I'd love to hear if any of you tried it before.