It looks like a different sort of bubble this time. If I recall, in 2000, not only had valuations gone ridiculous, but there were also a couple of big triggers

It looks like a different sort of bubble this time. If I recall, in 2000, not only had valuations gone ridiculous, but there were also a couple of big triggers for tech spending to drop -- phone networks globally (big spenders) had overbid on 3G licenses and wanted to keep their other capital spending down, and other businesses had just come through Y2K spending. And the public imagination had lost rationality (press talking about the new economy and price-to-earnings ratios not mattering, etc...) This time around there's a cultural bubble among engineers (everyone wants to do a start-up), some irrational unicorn-hunting, and a window where governments are weak to VC demands for the sake of an innovation agenda, (eg, Uber's making more headway on taxi regulations than would normally be the case). But little sign that tech spending globally is likely to drop any time soon. There is also a slightly sad split in that some of the biggest unicorns are technologically not very innovative (Uber, Slack) while innovation & high tech spinouts from research continue to be a less spectacular slog. But that seems a less worrying bubble for engineers (the number of engineering jobs should still continue to rise, as more and more of companies business models are defined by the tech they use, and so if they want to differentiate their business they need to differentiate their tech)