Is making a site or a business around other people's data (YouTube's, Vimeo's etc) a bit risky in the sense that if YouTube changed their policy or terms, or ju

Is making a site or a business around other people's data (YouTube's, Vimeo's etc) a bit risky in the sense that if YouTube changed their policy or terms, or just got arsey, and blocked your access you might be left high and dry? If I were an investor (which I'm not - no experience or skills in that area) I would be interested to hear your answer on that. What would plan "B" be if something like that were to happen?