If you are going run the tube then you can embed videos from the PH and other sources but I would recommend downloading content from them and uploading to yours, you might get the DMCA notices pretty quickly. The problem with the type of sites is that if you are going to give away lots of stuff (especially videos) for free then your users do not really have an incentive to buy anything and spend any money, thus you will not make money unless you have a lot of traffic. If you are going to start one, then at least choose yourself a niche so there is not that much competition and you can see some result faster.
