How do they make money

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Of late I have been noticing a lot of YouTube videos popping up in blogs, webpages, e-mails and newsletters. Videos use a lot of bandwidth. YouTube gets a lot of hits. I also have enjoyed watching Rocketboom, a daily vlog. Vlogs use a lot of bandwidth. Rocketboom gets many hits.
Many hits multiplied by bandwidth equals a lot of money to pay.
What I have not figured out is on how either of the companies make money. What is their business model? If anyone has a tip, please do share it.