That is a great question, in most cases. In my case it's a bit different. As I said in reply to Michael earlier:

I used to work with people that worked with ad agencies all the time. They always used to complain to me about this specific problem. It was something I had to deal with, A LOT.

I, personally, never dealt with the ad agencies directly. I have also spoken to a few people that work at various agencies and they have confirmed that this a problem. But those leads haven't worked out.

So it's not that I don't know the problem I am solving.

I have solved a problem that I know exists. Now I need to find the market that understands that particular problem and sell them my particular solution....if that makes sense.