That's one factor, and one that the investment community likes to play up. I'm not really sure this applies in the unicorn case, though, since the amount of mon

That's one factor, and one that the investment community likes to play up. I'm not really sure this applies in the unicorn case, though, since the amount of money that they're raising in the "private IPOs" they do dwarfs the reporting costs of being a public company. The biggest factor, in my opinion of course, is that some large private investors realized that they could capture most of the upside in an IPO before the IPO actually happened. The first real example of this is DST and Facebook. This has obvious advantages for the private investor -- they get access to a source of high quality risk for their portfolio. It also has obvious advantages for the company -- they get access to capital without having to manage to Wall St's expectations (and that's no minor thing). Facebook was sort of the proto-unicorn, and it spawned imitators. Those imitators were not just startups, it also spawned imitators on the investment side. Suddenly a source of relatively easy money -- the initial IPO allocation in "sure thing" companies -- weren't available to the usual suspects, and those funds have naturally followed the leaders into the D, E, and F rounds of the new breed of unicorns. These deals are even accessible to relative small fry now -- private bankers will routinely shop around access to these funding rounds to people with assets "only" in the 10's of millions. Sometimes they're shopping a theoretical deal that they want to present to the company in question, and sometimes they're shopping AirBnB. At any rate, many of the gains you used to be able to get in companies like Amazon or Google are now going to people able to get access to these pre-IPO deals. Financing private companies is very different now than it was 5 years ago.