A new report from eMarketer says that with 67 percent of Internet users already seeing some form of video advertising online (in-stream, in-banner, or in-text) at least once a month, the audience has reached critical mass and video ads will become “ubiquitous” by 2012.

By 2012, eMarketer predicts that 80.6 percent of Internet users will view video ads at least once a month. The report also forecast that 129.5 million people will view some form of online video ad at least once a month this year, with that number projected to grow to 183.3 million by 2013.

Among the factors contributing to the growth of online video ads is the increase in professional content, according to eMarketer analyst David Hallerman. Professional content will attract a “broad base” of viewers that will in turn attract marketers, he explains. Meanwhile, the increased availability of long-form videos like TV shows, web shows and sports on the web means more inventory in and around which to place those ads.

In July, a Diffusion Group study predicted that professional content would command higher CPMs than UGC vids and grab a larger share of the video ad market through 2013. In August, eMarketer predicted that the market for online video spending would hit a five-year percentage growth peak in 2012, hitting $3.4 billion.