A billion dollar company is founded every three months in Silicon Valley

Note - The original quote is from angel investor Ron Conway; essentially he's pointing out that there have been about 4 software-based companies founded each year worth over a billion dollars since the late 1990s
"Ron Conway once said: “There’s a billion company created every 3 months. Now, it is every 2 months”. I finally got the chance compile “The Billion Dollar” list. I tried to limit this list to only software tech companies. I also included a couple of near billion dollar companies (~0.7 B and above).
He was mostly right. Kind of.
There are about 4 billion dollar software tech companies founded every year, with the exception of 2000-2002.
There was a drought in 2000-2002 because of the dot-com bubble crash. Things started picking up again in late 2003 (Skype in Aug). 2004 became the return of the dot-com era (Facebook, Palantir, Yelp, Evernote).
Look around you. A billion dollar company was born within the last 3 months.
This means that there are about 8 companies in 2011 and 2012 that will become the next big thing. They are not big yet, but we will realize their value in years to come. I have included some companies founded in 2009 and 2010 that I think have the potential. It is much harder to hedge my bets on companies founded in 2011 and 2012."
Source:  MiniMing blog, 12th November 2012
E.g. -
2004 - Palantir, Splunk, Kayak, Facebook, Evernote, Yelp

2007 - Nicira, Gilt Groupe, Tumblr, Hulu, Dropbox, LivingSocial, Zynga

2010 - Fab, Instagram, Stripe, Skillshare