(1) Y2K doom merchants. If my memory serves me correctly, there was a plethora of self-proclaimed experts just before the year 2000 who published wads of bilge urging people to hoard food and build bomb-proof shelters in readiness for the collapse of the Western world. In fact a lot of this material can still be found on the Internet.
Well, my VCR didn't stop working, my car still started and I didn't notice any aeroplanes falling from the sky. The lights in my house still worked and no chaos broke out in the streets. Can't say I saw any toasters, washing machines or missile launching systems going berserk either. The only Y2K-related system failure reported in Australia was that of a bus ticketing system in Tasmania, which was duly repaired within a few hours.
In simple terms: most appliances or systems one is likely to encounter in everyday life either don't care what year it is or were already programmed with full four-digit year fields to begin with. It is true that a number of outdated software systems were updated or rewritten in readiness for Y2K, but the point is that plenty of warning was available and the necessary action was taken in almost all cases.
Do the doom merchants intend to refund the proceeds of their book sales to the people who were misguided by their hysterical writings? Have any of these writers dared to speak out publicly on any subject since 1/1/2000?
(2) Mysterious water heater that uses No Power. This is a really scary one. The description suggests that friction caused by the water supply is sufficient to somehow impart heat to the water in a capacity equivalent to a normal domestic hot water service. What an amazing apparatus - and launched in a regular newspaper catalogue without any fanfare or scientific accolades, too!
A more plausible explanation is that the water's flow drives a small turbine or similar, which provides sufficient energy to produce a spark which in turn ignites the supply of household gas to heat the water. So, presumably the text should explain that no secondary power source is needed for the gas ignition.
(3) Crop circles. Some English farmers already admitted they made the crop circles as a prank. The prank was quite funny. Crop circles are not made by mysterious intergalactic visitors. Get over it.
(4) Weasel marketing. I heard this story a few years ago and it may be an urban myth, but it makes perfect sense. Let's say you are a company offering financial services, and you have purchased marketing details for 600,000 potential customers.
For your first mail-out, you divide the group into halves (by any arbitrary means). To one half, you mail a letter stating that your company predicts interest rates will increase within three months; to the other half, a letter predicting an interest rate decline in the same period. After three months you determine which prediction was correct, and retain details of the 300,000 customers to whom you made it. (Forget the other half, they don't matter any more!)
You then undertake another mailout to the remaining 300,000 customers, this time about the exchange rate. As before, half will receive one prediction; the other, the opposite. Now after three months, 150,000 people will remain to whom you have now made two correct predictions.
Let's do it once again, this time with regard to - oh, let's say the stock market. And as before, you wait three months before evaluating your latest "prediction". You are left with 75,000 people who have received three (astoundingly) correct economic predictions in a total period of nine months. Predictably, these people are now in awe of your abilities and are lining up to be sold whatever financial products or services you have devised! Now, that's pretty sinister. Think about it...
(5) General illiteracy. In the latest advertising trend, people seem to have forgotten the correct spelling of "drawer" and replaced it with "draw". For example: "3-draw filing cabinet". Urk! (Don't worry, there are plenty more where this came from.)