As a rough estimate, I would say that approximately 95% of people you deal with are generally good, and try to do what is right; although they often lack the tools, knowledge, or understanding to know what is right. The other 5% of people are dangerous though, and will knowingly deceive you and act in an underhanded way to get what they want from you.
As often as people claim that politicians and sales men are in the 5% dangerous portion of the population, I think (with the exception of a few bad-eggs) most of them make ridiculous claims because the lack knowledge or understanding. When I was trying to help my sister buy a laptop I asked the salesman what the maximum resolution of the screen was and he responded with something like "Its 1000:1, the best you can get!" and I stopped asking him questions after that because it was obvious he didn’t understand what he was talking about; on a daily basis this guy probably deceives dozens of people with false claims because he doesn’t understand the product he is selling, and is too dumb to know when he should be quiet.
Personally, the only way I have found to protect myself against the 5% who are out to deceive you is to gain enough knowledge to understand what is "too good to be true." From my understanding, most people who will "rip you off" will take advantage of people’s inherent greed and make outrageous claims to sell people on something, Back when I was a security guard there used to be (probably still is) a radio show at 6:00 am on Sunday that was (essentially) the police informing people of popular scams in the area. One of the more popular scams was that someone would introduce you to an investment where you could earn a 1% or 2% return every week and convince poor people to put their life savings (or large sum of borrowed money) into the investment; and after they got enough money out of people they would close down and move to another area. In this case the police were having difficulty catching them because the scam artists were setting up and closing down so quickly that the police didn’t know they existed before they had committed the crime.
Basically, I wouldn’t consider myself cynical but I do have a healthy dose of scepticism about everything.
