GigaOm writes about a video talk by Jawed Karim:
Problem was, nobody used YouTube. Karim shows another video of the YouTube boys sitting around pondering their existence. Nobodys going to watch this, they complain; This is lame. To try to attract viewers, the three figured the best thing would do would be to get hot chicks involved. So, Karim recounts, they posted an ad on Craigslist in Los Angeles promising attractive females $100 if theyd post 10 videos on YouTube. They got not a single reply.
In June 2005, YouTube revamped, adding the four essential features that jump-started viral growth. 1) related video recommendations, 2) one-click emailing to spam a friend about a video, 3) more social networking and user interaction tools like video comments, and 4) an external video player.
That sharp uptick of growth (which, included in todays YouTube traffic chart of the last two years, shows up as part of the flatline days) made it possible for YouTube to raise $3.5 million in November 2005.