Copyright Legality?

Hi everybody. I have intentions of building a video website for news updates and have even purchased a domain name for it. However, i came across an article that has me thinking and halted all my efforts to go ahead and build this. In the article it said something like when you autopost videos to your blog form public places like youtube and vimeo you risk serious copyright stuff. My question is why would there be an embedd code if the videos are not intended to be shared? Then again i ask myself what if the videos are like say CNN, BBC, or MTV youtube page( I mean big companies who have a youtube channel and upload videos constantly) Can you autopost these videos, like immediately they are uploaded your wordpress plugin pools it into your website). Its just like embedding the videos but this time done by a plugin in your absence. I see many popular music video websites (worldstarhiphop etc)have youtube videos and i wonder how they get access to them. Are there any legal issues if the videos are not modified or anything , just posted to your website. I hope to get some serious answers. I'd be more thankful to people who have vidoe sites and wanna share their opinions.