Silicon Valley start-ups aren't known for soft-pedaling their products' virtues. This Californian Mecca of braggadocio runs on inflated claims, white lies and an ingrained culture of faking-it-till-you-make-it. Things usually pan out one of two ways for these swaggering upstarts. Either the company makes it big and changes the world forever - think Google, Apple and Amazon - or it falls on its sword after tasting defeat in a cutthroat market. But...