I think there are actually two aspects to the market question. First, there's the level of pain experienced by the customer, and second, there's the size of the

I think there are actually two aspects to the market question. First, there's the level of pain experienced by the customer, and second, there's the size of the market. Lots and lots of startups are solving "hair on fire" issues for relatively small markets - enough to generate millions in revenue, but not billions. For a sad case in point, there's not a whole lot of research for a cure (or even a treatment) for ALS - a disease that is completely debilitating and almost always fatal. There just aren't that many patients (even though it's common enough to touch famous people like Lou Gehrig, Stephen Hawking, and Jason Becker). Meanwhile, tons of money are poured into Viagra and its competitors - not an actual lifesaving problem, but a huge market.