The smartest people in the world attacked this question ("what do we use it for?") in the 90s, and nobody was able to come up with a killer app (as in, widely-applicable-once-mass-produced) then.
I don't know what's fundamentally different this time, which is why I'm skeptical that the outcome will any different.
So, uh, what is it? Have we figured out what to do yet after 10 years, 11 funding rounds, and billions of funding?