It's amazing to realize that even a monster success like Weebly (which among other things has made each of its founders vastly wealthy) is basically a roundoff error on Dropbox + Airbnb ($455m/($10b + $10b) = 0.02275).
This statement only applies to the founders, employees, and customers of the company. My point is that it doesn't apply to the investors: from an investor perspective, it doesn't matter if almost every company dies as long as the Droboxes and Airbnbs survive and grow. Almost all the returns come from a tiny number of outrageous successes, to the point where even a big hit like Weebly is a drop in the bucket.