University of Toronto researchers found that 45% of the immunization information on YouTube contradicts the official government recommendations in Canada. Those recommendations are very similar to the standards in the US.
I’m not trying to start a debate about whether or not immunizations are a good idea. However, it does point out how easy it is for any group with an agenda to post official looking medical advice on YouTube, and then work the system to get a bunch of positive reviews on the videos, thereby adding to their apparent credibility. Teens especially, who might be hesitant to discuss a potentially embarrassing medical issue with their parents, could be more likely to believe a highly rated and professionally produced YouTube video that is dispensing questionable medical advice.
Open and honest communication with your kids is the best antidote to this. Bad information has always been out there. The Internet makes it both easier to find, and easier to debunk.