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1.
Viral Videos are online videos which gain mass popularity through Internet Sharing, such as entertainment websites, e-mail messages or suggesting a friend watch it. Heavy.com and Youtube.com are two well-known examples of media sharing websites which contain viral videos.
"I posted this vid of me and my friends lighting off fireworks in our pants and its all over the web man"! his video has become a 'viral video'
by Sam Kn. August 29, 2006
 
2.
The term "viral video" refers to video clip content which gains widespread popularity through the process of Internet sharing, typically through email or instant messages, blogs, and other media-sharing websites, such as YouTube. Viral videos are often humorous in nature and may range from televised comedy sketches such as Saturday Night Live's Lazy Sunday to unintentionally-released amateur video clips like Star Wars Kid.

The proliferation of camera phones means that many videos shot these days are shot by consumers on these devices. The availability of cheap video editing and publishing tools allows video shot on mobile phones to be edited and distributed virally both on the web by email and between phones by Bluetooth. These consumer shot videos are typically non-commercial videos intended for viewing by friends or family.
Did you guys see that viral video on YouTube the other day?
by Melissa Nikol December 24, 2006