This is completely unfounded advice, and in my opinion, stupid advice. Ideas do get stolen, regardless of what you've read.

Do you know someone? Can you give an example of someone that was starting a business told someone the idea and that person went and ran with the business?

I believe that it may happen, but it feels like an urban legend - I've never actually seen it or heard it.

It does happen. Not as often as founders fear, but it does happen.

The writer would have been closer to the truth if he said that founders generally err on the side of secrecy.

"It does happen." I believe it has happened, but the whole point of the post is do you know anyone that this has ever happened to?

And if you don't know anyone this has happened to, how do you know that it actually happens?

A company claiming to be interested in buying Viaweb instead copied us (as well as they could) and went on to be very successful. They didn't kill us, because they were in Japan. But I expect they did make it harder for Yahoo to launch a Japanese version of Store.

This is a good example. I'm guessing you didn't only tell them the idea, you opened up your books, detailed plans and possibly even your code.

A potential sale situation is different from taking the first steps on the idea. You had already started building the company.

I think managing the disclosure of sensitive information is a totally different topic (one which I wish I knew a little more about).

It was so early that we had no books to open, and they were business guys who would not have understood our code if we'd shown it to them. All we did was explain what we were doing.

Facebook - http://www.aarongreenspan.com/letter/

As he said, he's talking about business ideas, not trade secrets. If your idea is not obvious, most people will think it's stupid anyway.

"Of course we aren't talking trade secrets we're talking business ideas, and ones that aren't glaringly obvious."

Glaringly obvious to who? Your start up idea might not seem glaringly obvious to you but don't assume it isn't to your competition!

Flying Cars.

Flying Cars? whats your point?

"Flying Cars" isn't a good answer to your question, agreed, but it is an obvious idea - to everyone.

Chances are that if you are starting a business and you have competition already that they have thought of your idea or something similar and chose not to do it for whatever reason.

My business is www.shelfmade.net - I am now friends with a guy at sharedbook.com. Look how similar the businesses are. I have told him my ideas and he has told me a good deal bout his company. As obvious as I think my idea would be to his company, they are just not into it. They are not going to steal the idea unless I first prove it - then they would know about it anyway.

(Sorry my thoughts are a bit scattered- don't directly address your question, but I'm sure there is a point somewhere)

What if the idea is still just an idea, and you plan to implement it but haven't started? There is no headstart in this case.

Talking to people will help you evaluate and refine the idea. Making changes and finding a market is really the beginning of "working" on an idea.