Our attention span is not very long. And with every new form of media humanity comes up with critics cry out that we managed to diminish it even further. Sometimes this is hard to deny. We have Vines. They are six seconds long. And we don't necessarily even watch those till the end.
In opposition to Vines, YouTube haikus are extremely long. Reddit-User buttkingpro3000 who seemingly invented the term defined them as "almost poetic video(s) under 14 seconds" (Vines are not included in this definition because they also derive parts of their form through other mechanics such as the filming via a mobile phone and the looping of its content while watching). If you look up examples on YouTube you will notice that most of these video haikus are between ten and 14 seconds long. Since Instagram introduced the possibility to publish videos with the length of up to 15 seconds you can find similar types of videos there too. We aren't interested to follow the 14-seconds-rule to the letter anyway, but it gives a nice guiding value to describe videos, which resemble the original idea of the literary haiku very closely. A Haiku is a Japanese poetic form. Most of the time these short texts consists of opposing or intertwining dispositions.
A youtube haiku, how we understand it here, is exactly that: A short video around 14 seconds, which consists of two dispositions. Their arrangement forces them to form a relation and this results in the sensation that buttkingpro3000 described as "poetic".
Since the beginning of this year (2015) we started to collect and publish those kinds of videos, which are often a spontaneous result of our work. We arranged them on one page in little video frames to give everyone the possibility to play them simultaneously and thus remix the material into something new every time they are watched (for our other experiments with non-linear editing methods check out our Cut Up videos here).
So go nuts. Or not.
Anyway, by reading all this you already proved that you have an attention span which is much longer than we expected: Congratulations!

EDIT, January 2017: Vine is dead, Instagram can play 1-minute-videos by now and YouTube doesn't just count clicks anymore, but also data mines the actually played seconds/minutes of your videos. And the youtube haiku? We moved them. Because, if we are really face it, we never really felt good with them on YouTube. Now they are just video haiku and thanks to HTML5 they are also looping like our vines once before. [CLICK HERE FOR LOOPING HAIKU... or down below on the picture if that does feel better to you]