Also, a lot of YouTube's audience are teenagers, who are on average worse than adults at picking up facial emotional cues:

> We tested older children, adolescents and adults on a two-alternative forced-choice discrimination task using morphed faces that varied in emotional content ... adults displayed more sensitivity to subtle changes in emotional expression than children and adolescents ... The results provide evidence for late developmental changes in emotional expression recognition with some specificity in the time course for distinct emotions.

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.469...