Generallization fallacies

Quite often, people seem to believe that some method, model or system of beliefs is good because they see instances in which it is good. This can be very false and deceptive, and it is sometimes used as a tool to spread and sell garbage. There are several traps involved here:

• Does even a part of it work reliably? It's easy enough to find a few examples which support something, but that doesn't prove anything. For example someone trying to claim that their stock picking scheme works has a huge amount of market data they can use to try to find good supporting examples. People can also deceive themselves because even a terrible model may sometimes fit reality through coincidence.
  
• If a part works that doesn't prove the rest. It's easy to package something accurate with a load of garbage and try to sell the whole load of garbage as if it was accurate. Some people will look at the accurate parts and conclude that everything under the same label is accurate.
• If something works and has a new name that doesn't mean it's unique. It's easy enough to try to market something as "new" or "secret". Sure, the idea might work but it might be overpriced and a deceptive source may deceive in other ways. It probably makes more sense to find a source which acknowledges the true history of the idea.
• Proprietary jargon can make something seem unique, sophisticated and special. Use of proprietary jargon can also draw people into a particular system. It is much better to use standard terms. They make understanding easier and open one up to many more sources of information.