One theory I'm currently fond of is that the band of growth where unicorns live ($100mil -> $1bil in valuation) used to be accessible to the public markets, but

One theory I'm currently fond of is that the band of growth where unicorns live ($100mil -> $1bil in valuation) used to be accessible to the public markets, but it's recently only become available to private investors. This creates weird distortions in investment behavior, because it means investments seeking this behavior have to trickle down to VC or acquisition. This could be way this comes about -- by investing in Google or Apple, you're effectively investing in a 10-year VC fund. Sure they're sitting on a lot, but hopefully they make enough acquisitions with it + "raise" enough more during that time that it looks like the cash is going to work.