One of Umair's refrains is that Silicon Valley types are often overly enamored of raw [or novel, in the pejorative sense] technology that isn't directly serving people's [or society's] biggest problems NOW.
That's a rather shortsighted criticism. Large things start small, and often solve problems in an indirect way. YouTube probably didn't look like something that would "serve society's biggest problems", but it does just that (by giving more people a voice, exposing corruption and abuse, etc).
Well, I would say that I agree with Umair that YouTube did indeed solve a huge personal/social problem (reinventing the stale, inefficient television/video value chain). Right off the bat, too.
I also agree that "large things start small", but which of these companies do you think really have potential to create enormous value for millions of people?
ZocDoc? Zivity?
I'm just playing devil's advocate here...I hope some of these companies really knock it out of the park, but the roster is a little "underwhelming" on paper.