How else would you define worth, besides "what someone is willing to pay"?

Please explain why taking into account sudo comparable sells/offers such as Slack, WhatsApp, etc.

EDIT: As noted below in the comments, LinkedIn was bought for 26 Billion in cash by Microsoft.

Why are any of those worth over a billion? Valuation should be assets - debts + future profits. In reality, mostly, it's psychology + voodoo magic - negative press.

I used to think this way, then I spent the last decade watching my friends all get rich working at these kinds of companies.

You need to look at the big picture here. Young people aren't watching TV. Ad spend by the likes of P&G, Nike, and the auto industry is still largely on TV. Also, Silicon Valley largely hasn't been able to capture brand advertising -- the spend on billboards, sports stadium advertising, etc vs. direct-response like Google AdWords. Ask anyone in the industry， they'll tell you direct-response spending is a drop in the bucket compared to spend on brand advertising.

Now, tell me, one the ad industry wakes up and realizes how absurd it is to dump billions of ad spend onto a platform with rapidly declining viewership (linear TV), where is all that ad spend going to go?

Maybe a communications platform that's used heavily by young people (great for advertisers), to send pictures and short videos (ads?) to each other in a playful, unhurried manner?

I don't know whether that's worth $20 billion or whatever its "valuation" is, but these dumb cheap shots against ad supported tech company valuation need to end. These platforms are as big as like, several big TV networks combined in viewership, with about 100x better ad targeting. How isn't that worth billions?

"How isn't that worth billions?"

ad blockers

I wonder if a "scorched earth" plan could be pitched to old school TV advertising giants, in order to score billions for adblocker research. Adblocking has "needs AI" written all over it.

The point is that there won't be an all-cash 17bn transaction for Snapchat. I'm unaware of a SV startup sale in that dimension which happened in mostly cash. Usually, and I may be missing some deals, it's part cash and mostly shares of the buyer.

LinkedIn, while not really a startup, was an all cash purchase.

Interesting, do you have a source for that? All I recall is that LinkedIn is struggling and it's hard to understand why MS would pay 26bn (http://www.recode.net/2016/6/13/11920416/linkedin-acquisitio...).

"Microsoft Corp. (Nasdaq: MSFT) and LinkedIn Corporation (NYSE: LNKD) on Monday announced they have entered into a definitive agreement under which Microsoft will acquire LinkedIn for $196 per share in an all-cash transaction valued at $26.2 billion, inclusive of LinkedIn’s net cash"

http://news.microsoft.com/2016/06/13/microsoft-to-acquire-li...

You could do all the comparables you want in 1999. That doesn't mean valuations were justified then.