Great article by Mark Richards, proposing a technique for identifying tough, valuable problems that could make you a lot of money:
The value of a problem directly correlates to the time people will take to tell you about it.
Time and time again we find that if busy people, who fit your target customer profile, are willing to give you valuable time simply to discuss a particular problem, with no clear promise (yet) of a viable solution, then you have an important problem. The kind of problem a startup, with limited resources, no brand, an incomplete product and a small team can actually sell into.
Worth reading the whole article. I'll keep an eye out for more good stuff from Mark, he seemed to be planning a follow-up to this, though it hasn't been posted yet (the article is from September 20th).