How can you design a product for your customer if you do not know your customer, the business domain, and the technology you are building with? People do it all the time.

How many technologists have the coolest latest thing that they are searching for a market and a user?

How about the designer who had the most awesome solution that cannot be built within years or millions of dollars?

Or the product manager who knows better than his users what they need and will get development to build what he wants?

We all work with or know people who work with these situations. A solution needs to meet the users needs and desires, fit the market and be sellable, and be produceable with the technology and expertise at hand. Creating a solution with all three aspects provides the best start to delivering a profitable solution that people want.