According to recent figures from comScore, YouTube is absolutely dominating the realm of online viewing:
Google sites were the clear winner in online video, with 120.8 million unique viewers. According to comScore, 120.3 million of those viewers were for YouTube.com What may be more shocking is the average number of video per viewer: 134.9. That’s nearly 5 YouTube videos per day. A lot of this can be attributed to embeds, which may not be reflected as unique traffic on YouTube.com.
(YouTube is categorized as “Google Sites”.)
The next highest average number of videos per viewer is Viacom’s 19.2, which makes you wonder exactly how any competitor will dislodge YouTube’s command of the space.

