Well, another way to put it is that you come up with ideas and only others can validate them into opportunities. You can't turn an idea into an opportunity. The market, your customers, determine if there's an opportunity in it somewhere.
But I'll reiterate what I said about opportunities: The can and do exist in the complete absence of ideas.
The value is in opportunities. There are people who would love to steal your opportunities. They don't give a shit about your ideas. That's too much work. They want you to hand-feed them the juicy opportunities. It's almost like the difference between R&D and just "D". The first is hard. Once the "R" is done, the "D" tends to be a lot easier to execute brilliantly.
I have a database of probably about 600 ideas accumulated over time. Most are probably crap. No market opportunity. I am in the habit of logging ideas without passing any judgement at the time they are generated. Why? The Pet Rock. As my wife likes to remind me, I am to fucking smart to have ever considered the idea of selling rocks as pets in a little box. And she is right. So I try to not judge ideas until I really take the time to evaluate whether or not an opportunity exists.
As I navigate through my idea database and start testing them I start to discover the ones that might represent real opportunities and focus on them.
Sometimes opportunities require a lot of work to validate. An example of this are most iPhone apps today. You get two days, maybe three in the "New" list under your category and then it's a quick trip to page 253. Invisible. Gone.
Does that mean that there is no opportunity in application x based on idea y? Not necessarily. Having an app published on the app store is not validation, it just means that your app is now available for others to see, if you can get them there. In order to validate the idea you have to now do the legwork to create awareness and bring people to your app. Only after a real effort to get hundreds or thousands of people to have a look can you honestly say if your idea for an app that does x represents a real market opportunity. Some get lucky and take off on day one. Hardly the norm, of course.
This, BTW, as a developer, is one of the most frustrating aspects of dealing with people who approach you with app ideas. They don't understand that thinking that something is great doesn't mean that a million people are going to run to buy it.
A case in point is this guy who approached me about doing yet another storybook for kids. There's a million of them out there. Great idea right? The market opportunity is certainly validated. Right? Lots of people buying them. Right? Well, no. Not really.
The other element of this that hasn't been discussed is barrier to entry or barrier to market penetration. Sure, you can come up with a new series of children storybooks with great art, voicing, interactivity and music. The idea and the opportunity are identified and validated. The problem is that it will cost a bundle in marketing to unseat the top ten or top five sellers in that category. An absolute bundle. So, even though a market opportunity exists the idea and the opportunity are nearly worthless unless someone comes in with a truckload of money to make it happen.
When the guy asks me to do the dev work for 10% of the revenue...well, thankfully I can multiply by zero at blinding speed. No thanks. I told him that I'd do it for 25% and a non-refundable revenue advance payment of $50K upfront. He left. That was me using my Jedi powers to have him leave me alone.