Viral.

http://www.youtube.com/watch?v=VF9-sEbqDvU

One thing that I have always found curious is how and why exactly internet videos go viral.
People have had a fascination with short video clips since the technology of video cameras became easily available to everyday people, as shown by TV programs such as America's Funniest Home Videos and more recently Tosh.0. People, including myself, derive endless amusement from clips of funny animals, stop motion animation, or people humiliating themselves (among other things).
Obviously, the first step in a video's journey to becoming viral is it's creation. Someone must either think up an idea, like in the link that I posted, or just happen to be filming something. Again, obviously, the next step is for the person to post it online... but what happens after that? Is it as simple as sharing it with friends, who share it with their friends, and so on? And if so, how long does it actually take for that to happen?
I also wonder where the term 'viral' came from, in terms of internet videos. When I think of the word, I usually give it negative connotations like sickness and disease... but in the world of an internet video-poster having a video go viral is possibly the best thing that can happen.