On Friday, YouTube announced that it would no longer permit ads to run on anti-vaccine videos.  

Buzzfeed reported that YouTube said that anti-vaccine videos violate YouTube's policies on dangerous and harmful content.  Buzzfeed quoted a YouTube spokesperson as saying, "We have strict policies that govern what videos we allow ads to appear on, and videos that promote anti-vaccination content are a violation of those policies."  

YouTube's policies do not allow advertisements to be placed in conjunction with a variety of content that it says is not advertiser-friendly, including videos involving:

• Controversial issues and sensitive events;
• Drugs and dangerous products or substances;
• Harmful or dangerous acts; 
• Hateful content;
• Inappropriate language;
• Inappropriate use of family entertainment characters;
• Incendiary and demeaning content;
• Sexually suggestive content; and
• Violence.

This move reflects YouTube's recognition that advertisers continued to be very concerned about the environment in which their advertising runs.  Advertisers don't want to be associated with content that they believe could reflect poorly on the brand -- and many react quickly by pulling advertising when they believe that the advertising environment could put their image at risk.