You're over simplifying things. It's often not easy to determine what people want, because often people cannot say. For example, an iPod.
For example now, you have gotten stuck on this idea of condom cases. I personally don't want anything near to that. BUT, if the design were really interesting, I may want it. So you can't research if I want that, because even if you asked me, the answer I would give would be ambiguous.
Business School people come out with this idea that you can find out what people want before you have a product on that market. You can't! What you can do is identify a PAIN and fix it. You can identify something to be OPTIMIZED and fix that. If your product does not clearly fit any of those two categories, then all you can do is GUESS that people want it, then throw it at the market and move with the market to take the product in the correct direction.
It's easy for you to say condom cases are wanted after reading the article, but a condom keychain or case does not solve any specific pain. It's somewhat convenient thing, but I can easily live without it. It can work in the market, but it may not work.
The correct approach to this type business is to guess the best possible product that could sell in the market. Then put it in the market, and the market will tell you what it really wants. Then you modify to fit the market. But you have to factor this process into your finances, and you have to factor the risk factor in. The more unclear your market is, the greater your risk factor, and your finances have to be large enough to accomodate this risk. This was not true for the guys case above.
You are running with the wrong attitude if you think you can get things right all the time on one shot if you do proper research. It can happen, but most businesses will refocus after being on the market, and there are many many business who did the research, but didn't get it right. They failed and you never hear about them.