There are some good examples out there of difficult-to-understand buys and misunderstood valuations- there's no way the WhatsApp purchase is ever going to recoup its costs(the userbase is irrelevant, at a $1 per year price it just isn't gonna happen, especially considering the WhatsApp founders claimed they weren't going to be charging any more than that or for many other services they wanted to provide, AND that they wouldn't have ads), King.com is just this year's Zynga(news to the tech investment scene: The games industry is not nearly as simple as you seem to think it is), and there's no shortage of questionable investments in smaller companies, to be sure.
But then, you use examples like Airbnb and Oculus as an example of tech industry madness?
"Airbnb is like a hotel chain without the hotels." Yeah. That means they absolve themselves of costs, growth time, investment into that growth, location issues, the works. They hacked the concept of a hotel, and found the holy grail for that market space. Frankly, if you think $10 billion is a ridiculous number, with them being worth more than Hyatt- I'd be inclined to wonder what holds them back being worth 3 Hyatts. They've got momentum, they've got product, and they've got the community. Short of the possibility of some grand competitor actually coming in and doing a bangup job, I think Airbnb's potential is at least an order of magnitude higher than this.
And Oculus- so they have little revenue now? They have decent revenue at all for a product that has only been released to developers. You even admit that VR can completely change the world, but don't do the homework to understand they're probably less than 2 years from a product release with massive community and business support? What, did your deadline come up and you just had to submit?
Look, it's fine if you think either are overvalued. But trying to use either in your examples for how we're in a 1999-style bubble is laughable. You hand us two of the best reasons we're not in a bubble and wonder why everyone thinks we're not. Really now?