YouTube says it’s their birthday today, so I’ll wish them.
Happy Birthday, YouTube!
However, a WHOIS lookup shows their domain being registered on the 14th of February 2005. I guess their official launch was on 17 May 2005.
Look here: http://whois.domaintools.com/youtube.com
And the people at Mashable had already wished them on the 14th of February 2010. Take a look at their Happy 5th Birthday, YouTube! post.
YouTube.com is the biggest online video community in the world. It is the second most expensive company that was bought over by Google, the first being DoubleClick. The acquisition was done on 9 October 2006 for US$1,650,000,000.