London, England (CNN) --  YouTube this week announced the biggest viral video sensations of 2009, with Scottish singer Susan Boyle topping the list.



The most pressing question for aspiring video creators: How do you repeat that kind of success?



Value in views



Topping the YouTube charts brings significant value -- Boyle's clip had more than 120 million views on the site. Had the parties involved negotiated an ad revenue split (they initially did not), a not-inconceivable $10 cost-per-thousand-impressions would have yielded revenue in excess of $1 million.



When a clip has a commercial purpose, the brand value may be significantly higher: Evian's Roller Babies ad ranked fifth, with more than 27 million views, and the company says the campaign's success slowed its sales decline.



A commercial impact was also felt in the case of the JK Wedding Entrance Dance (more than 33 million views). The clip, which features a wedding party dancing down the aisle to Chris Brown's "Forever," sent the track rocketing up the iTunes charts.



What are the commonalities here, and is there a formula for viral video success? A definitive answer is infuriatingly absent.



The cute factor



The cute factor is perhaps the most prevalent trend among popular YouTube videos. In YouTube's most-viewed videos of all time, you'll find such adorable clips as a boy biting his brother's finger (140 million views), a baby laughing hysterically (100 million views), a sneezing panda (46 million views) and even the Evian ad.



The explanation is simple: When a clip makes us happy, we feel compelled to share that sentiment with others.



Humor



If our willingness to share is based on our emotional reaction to a clip, it follows that humor ranks highly on YouTube. From Jeff Dunham's ventriloquist act "Achmed the Dead Terrorist" to the obscure humor of "Charlie The Unicorn," laughter is a common theme.



In some cases, humor is not the intent: Tay Zonday's Chocolate Rain has surpassed 45 million views, our amusement (and discomfort) deriving from Zonday's utterly bizarre performance.



Comedy has geographical limitations however: What's funny in one country may be unfathomable in another. This perhaps explains why laughing babies consistently outrank standup comedians: funny doesn't travel.



Emotional response



Not every popular clip evokes laughter -- performances from Susan Boyle and Paul Potts tug at the heartstrings. So too does the Free Hugs campaign --  a music video featuring an Australian man giving out "Free Hugs" to strangers in public places has received more than 53 million views.



Music



Music videos are by far the most viewed content on YouTube. Had YouTube not created a second list to highlight top music videos on the site, these would have dominated the rankings for 2009.



The knowledge that best-selling artists rank highly on video sites may be of little utility to aspiring YouTube stars -- except to note that dancing videos and "lip dubs" have proved popular. With 132 million views, Judson Laipply's Evolution of Dance is a breakout success.



Cumulative advantage



Is the quality of the clip the only factor affecting its success? Or could it be that the rich get richer, even in the seemingly egalitarian world of YouTube?



Since most YouTube users head straight to the site's "Popular" page, clips that show early promise may continue to gain momentum for weeks and years. This process of cumulative advantage may help to explain why one laughing baby shoots to the top of the charts and another giggles in obscurity.



No formula?



It may be the case that there's no simple formula for YouTube popularity. In fact, it may be that the only true guarantee of success is novelty. The unexpected, the bizarre, the humorous, the offbeat, the emotionally affecting -- these authentic elements are hard to bottle, and fakes are easy to spot.



What will be YouTube's breakout video of 2010? We'll know it when we see it.
When a clip makes us happy, what do we want to do? What is the only guarantee of success? What brings significant value to advertisers and video producers? What may be the only guarantee of success? What might be the only guarantee for a successful YouTube video?
feel compelled novelty. Topping the YouTube charts novelty. novelty.
question: When a clip makes us happy, what do we want to do?, answer: feel compelled | question: What is the only guarantee of success?, answer: novelty. | question: What brings significant value to advertisers and video producers?, answer: Topping the YouTube charts | question: What may be the only guarantee of success?, answer: novelty. | question: What might be the only guarantee for a successful YouTube video?, answer: novelty.