Facebook doing things that don’t scale: each video ad will be pre-screened by 500 viewers

[BTW, I don’t mean that pejoratively.  It’s a reference to a popular blog post by Paul Graham, of ycombinator]:

Each video will be screened before it airs by a panel of about 500 viewers, who make up a representative sample of Americans. They will give the 15-second videos a score to reflect how much they like them. Only videos that score highly will get onto Facebook’s video ad platform.

Facebook Video Ads Ace Metrix Screening Creative – Business Insider.