"...what if you're not an expert on anything, i.e. you don't have a problem of
your own to solve?"
The question goes to the the heart of the point I was trying to make, since this is what so many young entrepreneurs with limited professional experience ask themeselves. While it's true that you might not have the professional experience to cater to enterprises, you have plenty of experience as a consumer to cater towards consumers like yourself.
Everyone is a consumer, so there's no excuse to say that you don't have expertise in anything. For example, if you spend 3 nights a week going to restaurants and night clubs, you start to get some idea of what makes a good menu or entertainment venue. If you go to coffee shops a few times a week, you begin to develop some expertise in what people are looking for in terms of atmosphere, music, service quality and product offering. If you like to explore new bands, but have trouble locating these emerging groups in your local Virgin Megastore, you start to gain some idea of a need that exists for people looking to explore new music based on their current preferences. The list goes on and on. As a consumer there's a pretty big chance that you have some sort of consumption pattern that makes you knowledgable in some areas, and it's these areas you want to focus on (if you'll notice by the way, I'm positive you can think of someone who has made money off each of the ideas I've listed above in the last 12 months.)
Of course the difficulty of innovating towards consumers like yourself is that consumers are innovating all the time. Our lives in the new millenium are so comfortable thanks to technology and e-commerce that we don't even have to get off our lazy backsides to purchase bread and milk (it's all delivered to your house! and if you don't like it, free return shipping!) But that does not change the fact that there's always room for improvement, and that there's always a pain point somewhere (it's human nature to never be satisfied!)
I find it highly unlikely that anyone 'doesn't have any problems' anywhere in their lives (if this is the case, my recommendation is not to bother reading this blog and starting a business, but rather taking it easy on a beach somewhere.) The trick is being persistent and always keeping your eyes open for a potential need. This means that you don't get much time to just shut down and lie down in the sun without analyzing the hell out of everything, but hey, that's the life you choose as an entrepreneur.
And if you really are living a life where you can't find a single need as a consumer... start changing your lifestyle to open you up to some new experiences; you're bound to find something somewhere out there. Just make sure you live it before you act on it.