It's time to replace the unicorn as a symbol of startups valued above a billion dollars, and so I'd like to suggest the oil derrick.

It's analog and very last century, but at least it exists outside of fantasy. And what image better conjures the tirelessly churning, seemingly endless quest for real liquidity from these privately held startups than an oil derrick? It seems every year for the past few years has begun with predictions that a gusher is finally coming for tech IPOs. And yet, each year, the well remains dry.

So far, 2018 is no different...