Did anyone consider that maybe Sequoia, who have invested in companies that make up over 10% of the NASDAQ know what they are doing?
Companies like Color, AdKeeper and Flipboard have "crazy" valuations based on the founders having ridiculous resumes. They have all created billions of dollars of value for their investors, hell, why wouldn't you invest in that potential again?
Rationalising this metaphorical bubble to domain prices is absurd, since domains have always been traded for eyebrow raising prices. You think that the domain color.com or path.com will be worth $10 in 5 years time? Seriously?
Color almost certainly didn't require $41M to get to the product you see today, did people ever consider the company is - gasp - launching early and has the capital to iterate and scale for the next few years? I can think of lots of startups that raised $10M - $20M at company formation and has then spent the next few years (or more) iterating.
Investors are less interested in where you are today, compared to where you are going