Good article! I think the unifying explanation is that too many funded ideas have failed to deliver the anticipated performance. As a dissertation writer I think a slowdown in investor exits is an effect of this, not the cause. Nonetheless, it certainly casts more attention on the VC compensation model on the part of those who invest in them. One way to invigorate venture-stage investing is to, as you point out, make it potentially more profitable for investors, private and public. Little can be done to reduce failure risk, but there is opportunity to reduce valuation risk.