Flymob

"Facebook has already been telling its video advertisers to hit people with faster messages. Sandberg said on the call that 6 seconds emerged as an ideal ad length in a recent test conducted with Tropicana."

http://adage.com/article/digital/facebook-brands-ready-6-video-ads/309929/

Facebook Gets Brands Ready for 6-Second Video Ads Facebook released second quarter results and outlined all the ways video is changing the social network, including forcing advertisers to create shorter ads.