I'd just like to point out that the "why now?" question is probably related to a major shift in America's monetary policy. Since the 2008 crash, the Fed has been using a policy of "Quantitive Easing" (QE) to keep interest rates artificially low and thus encourage lending and spending. It's been known for while that the Feds were looking to end this policy sometime this year and it's looking like the end of October will be that time. Although the Feds seem to indicate that they won't actually raise interest rates until sometime next year, halting QE will have the affect of making less money available for lending. No one is really sure what is going to happen but this is an event that will affect the economy as a whole. To me, it's sounding like one of the industries that could be particularly affected by this policy is Tech and the result will be a market correction in startup valuations.
Links! http://www.investopedia.com/terms/q/quantitative-easing.asp http://www.economist.com/blogs/economist-explains/2014/01/ec... http://www.forbes.com/sites/investor/2014/09/23/the-end-of-t... http://blogs.wsj.com/moneybeat/2014/08/05/goldman-sachs-here...