For those wondering why, check out slides 14 and 15 of the 2013 KPCB Internet Trends report:
http://www.slideshare.net/kleinerperkins/kpcb-internet-trend...
http://www.slideshare.net/kleinerperkins/kpcb-internet-trend...
Edited to add: Not to mention that they have a captive audience--you'll have to watch the ad, which I have to think is prime ad space that they can charge for.
http://www.businessinsider.com/venture-capital-kingpin-klein...
Everyone looks at these kinds of things with wide eyed astonishment. We are talking Pets.com era stupidity in valuations.