This week's Trends: anniversaries, webcams, and the future

Each weekday, we at YouTube Trends take a look at the most interesting videos and cultural phenomena on YouTube as they develop. We want take a moment to highlight some of what we've come across this week:

• We looked at how the anniversary of 9/11 became a dominant topic on YouTube.
  
  
• We studied the unexpected pop-culture resurgence of Back to the Future 2.
  
  
• We tracked the popularity of iPhone concept videos.
  
  
• We saw some interesting public displays from around the world.
  
  
• We collected dramatic footage from a chemical fire in Canberra.
  
  
• And these two seniors trying to work their webcam became the major viral hit of the week:

Check back every day for the latest about what's trending on YouTube at: www.YouTube.com/Trends

Kevin Allocca, YouTube Trends Manager, recently watched "You're not gonna be the great breakdancer you think you are."