Youtube promotes trending videos, so if you get a lot of views very quickly, particularly among a common demographic, then the video will be more heavily promoted, and is more likely to go viral.
Similarly, videos with lots of view tend to appear higher in search results.
I imagine that people at youtube are very aware of this, and put an effort into distinguishing ``real'' view (consistent demographic/trusted referer) and ``fake'' (spammy/ black hat SEO) views.
"Somebody that I used to know" likely hasn't been seen by 100M people, but the people who have seen it keep watching it. Over, and over...