When a work, such as a video, is uploaded onto YouTube or a
photograph uploaded onto Flickr, people often believe that because
it is being made available on the internet, it is free for them to
download, distribute or use. This is a common misconception and
what many people don't realise, is that, more often than not,
copyright vests in those particular works. Unless you have been
authorised by the owner of the copyright (for example, in the form
of a license), you cannot simply do what you want with the
work.
It's vitally important to ensure that when you are using or
downloading works from content sharing and knowledge-based
platforms such as YouTube, Flickr and Wikipedia, you have the
authorisation or license to do so (or, in the alternative, to
ensure that the work or content is not protected by copyright). One
way to do this is to see if a Creative Commons license has been
assigned to the work or content, before downloading or using the
work.