I recently ran across a tutorial where the instructor used this syntax:
display: -webkit-box;
http://www.youtube.com/watch?v=B-MNkBh7F2A @ 2:30
I think this topic summarizes it the best: http://css-tricks.com/old-flexbox-and-new-flexbox/
Basically Flexbox has 3 different "iterations" of the markup. The old 2009 markup, the still old 2011 markup, and the "new" markup which isn't officially released or supported yet.It's important to note that despite the video you linked to being uploaded in 2012, the guy who made the video is using the really old 2009 implementation of flexbox. I would suggest NOT following that tutorial.
Here are some more resources: http://www.w3.org/TR/css3-flexbox/ http://dev.w3.org/csswg/css-flexbox/
And Can I Use it? http://caniuse.com/#search=flexbox
the -webkit-box is the latest and saves so much time on using the old style which requires a lot of javascript ,so in designing with the webkit you are producing your work to the latest standards and a big saving on man hours.