Examples are great as long as they bring the reader's knowledge of what you are talking about to a point where they can have a level of understanding of what you are trying to explain.
Back to the Basics
In the "Basics" section I touched on the need to determine your audience. Determining who your audience is gives you a good handle on what examples to use.
If I am writing to a bunch of car enthusiasts I can assume they know what a carburetor is and how it works. But there are audiences out there that think the word "carburetor" is a French word meaning "leave it alone" and I have to agree with that group. *grin!*
But if I really need you to understand how a carburetor works, I have to find something common that I can relate it to, like say a toaster. Here's where this example just fell flat on its butt.
My husband is a mechanic, which was why I chose the example of a carburetor, because he talks about things all the time that I pay zero attention to. I don't need to know how an internal combustion engine works in order to drive a car.
So, thinking this was a wonderful example, I called my husband in from the other room and asked him how I could explain a carburetor to a bunch of people that didn't know what a carburetor does. He gave me one of his patented looks. I knew I was in trouble.
He explained to me patiently that he can explain how a carburetor works, BUT he cannot relate it to anything common like a toaster to get a starting point from which to explain it.
I picked a really bad example, but rather than toss this out and try and find a better one, I'm leaving it here to show you that sometimes what you want to explain to someone is more complex than it's worth. At that point, you had better be writing to a very narrow audience of car enthusiasts.
Examples that are Useful
Effective examples that are useful (unlike the one presented above) are the ones that bring the level of understanding of your audience up to a level where you can explain something more complex that builds on what you believe they know.
If I am trying to explain how to create a complex table to be used for a presentation at a website, I have to assume that the reader has the level of understanding necessary to know how to create a basic table. Rather than assume, to be sure that my reader has that level of understanding, I can quickly use a basic table as an example, and at that point I have not insulted my audience, but only made sure that the reader had a place to start before reading the rest of what I wrote.
Don't Insult Your Readers
Insulting your readers is the last thing you want to do! Use examples to illustrate your points but don't over-use them. If you have several good examples that all illustrate a point, pick the best one. Boring your readers with example after example will have them saying, "I get it! Move on already!" and wishing they had never started reading what you wrote. Your readers are investing time when they read what you write. Once that time is spent, it cannot be recovered.