If all startups face the same problem then the strongest startup wins. Simply naming a risk that all startups face and then saying the strongest startups in their respective domains are more at risk isn't really cutting it for me. If there's anyone that would figure out how to store my files in the cloud reliably it's probably dropbox and if there's anyone that's going to solve the math, science and cs problem of moving cars around...it's probably uber and not lyft or any of the other competitors. For now, their $ Billion valuations are safe and sound.