YouTube was founded by Chad Hurley (who studied design at Indiana University of Pennsylvania), Steve Chen and Jawed Karim (who studied computer science together at the University of Illinois at Urbana-Champaign). They were all early employees of PayPal, and had developed the idea for YouTube during the early months (February) of 2005.
This video-sharing website allows users to upload, view and share videos. Its technology used to display a large variety of user-generated video content like music videos, movie clips, TV clips and blogs, are Adobe Flash Video and HTML4 and 5.

Any user can watch videos, while registered users can even upload an unlimited number of videos. Videos considered to contain offensive content are available only to registered users at least 18 years old.

In November 2006, YouTube, LLC was bought by Google Inc and became a subsidiary of Google.

Facebook is a social networking service founded by Mark Zuckerberg with his college roommates and fellow students Eduardo Saverin, Dustin Moskovitz and Chris Hughes, launched in February 2004, operated and privately owned by Facebook Inc. Statistics showed that nowadays in February 2012, Facebook has more than 845 million active users. In the process, users must register before using the site, after which they may create a personal profile, add other users as friends, and exchange messages, including automatic notifications when they update their profile. Also, users can join common-interest user groups, organized by workplace, school or college, other characteristics, and categorize their friends into lists such as “People From Work” or “Close Friends”.

Facebook allows any users who declare themselves to be at least 13 years old to become registered users of the site.
The Web site’s membership was initially limited by the founders to Harvard students, but was expanded to other colleges in the Boston area, the Ivy League, and Stanford University. It gradually added support for students at various other universities before opening to high school students, and eventually to anyone aged 13 and over. However, based on ConsumersReports.org in May 2011, there are 7.5 million children under 13 with accounts, violating the site’s terms of service.

A January 2009 Compete.com study ranked Facebook as the most used social networking service by worldwide monthly active users.
Entertainment Weekly included the site on its end-of-the-decade “best-of” list, saying, “How on earth did we stalk our exes, remember our co-workers’ birthdays, bug our friends, and play a rousing game of Scrabulous before Facebook?”