Is it advisable for a startup to focus much of its marketing content on the 'problem' it is trying to solve?

Well, whether you spend a lot of time educating people on the problem depends on the product itself. If you're doing something completely unique, education should likely be a larger part of your marketing mix. However, if you have a mobile app startup that lets people tend to their virtual farms, for instance, that's another story. While it's a gross oversimplification, in my experience a typical startup goes through 3 major phases in their marketing communications. And by the last phase, they are hopefully not a "startup" anymore. 1st phase, Innovation: This is when you tend to focus more on your innovation and the problem it solves. At this stage,"proof" is less important. This stage can last several years for many companies. 2nd phase, Proof: In this stage, you goal shifts to showing proof of the impact of your innovation through customer success stories and verifiable metrics on your impact against the touted product benefits. Sure, you need proof in Stage 1 too, but it's not the primary focus. Here, you move away from talking about your disruption all the time and instead hammer home how real users are benefiting. 3rd phase, Sustain: In this stage, your communications shift to focus more on company growth, revenues, market leadership, etc. Here, your goal should be to validate that you are making the proper operational and product shifts to manage customer demand and business growth, assuming you've survived Phases 1 and 2. Again, these steps are very generalized and will vary considerably depending on whether a startup is B2B or B2C. However, I've found them to be helpful when thinking about how communications should shift as a startup matures.

There is only one marketing strategy: Understand your prospective customers' wants and needs, then adapt.  If they aren't searching for a solution to the problem you solve, then selling the problem should be your primary marketing focus.  See Seth Godin on this topic: http://sethgodin.typepad.com/seths_blog/2010/08/sell-the-problem.html

I think you should put it in this way: we are focusing on the problem business are trying to solve, and tell your prospects what you can do for that problem.  So it is not just focusing mainly on problem, but focusing on how this problem is solved by your unique solution/