Build apps not businesses.
DHH doesn't lambast side projects, doing things for fun or even giving things away - Rails is the obvious proof of that. DHH lambasts the weird aversion we software guys have to charging money for things.Absolutely build apps for the fun of it, feel free to scratch your own itch, but if you build a useful product, try charging money for it before you give it away for nothing. If nobody wants to pay for it then you can always GPL your code and hope for the best, but releasing software under Free licenses by default robs you of big income opportunities.