Roughly 152 million individuals living in the United States (or almost 49% of this country’s population) watched a YouTube video in the month of January. And about one in every six of those individuals who watched a YouTube video watched one from Machinima.com.

According to the latest numbers from comScore’s monthly US Online Video Rankings, the “next generation video entertainment network for videogamers” that garners over one billion views a month worldwide, captured the attention of 23.8 million unique video viewers on its YouTube channel last month. That accounts for roughly 15.66% (or about one in every 6.38) of all of YouTube’s unique monthly video viewers. That percentage is up close to 1.2 points from December, when Machinima’s viewers accounted for somewhere in the ballpark of 14.46% of YouTube’s total.

Despite the slight uptick in YouTube share, Machinima is in a solid third place on comScore’s Top YouTube Partner Channels Ranked by Unique Video Viewers. Music videos still reign supreme in terms of viewership, with Vevo maintaining the number one position with 50.6 million unique monthly video viewers (or about one in every three YouTube viewers), followed by Warner Music with 29.7 million monthly uniques.

In advertising analytics news, US consumers watched 5.6 billion online video ads in January. That’s a post-holiday slump of roughly 1.5 billion from the 7.1 billion online video ads consumers were subject to in December. That may seem like a big dip, but the numbers are  little cause for alarm. Q4 is traditionally a huge quarter for advertising spends and if you look at the amount of online video ads viewed in Janurary 2011 compared to January 2010, the industry’s up 28% year over year.

Check out more online video-related stats and figures at comScore.