I see this sort of plagiarism occur all of the time, for all sources of media and from different mediums. Very often without any sort of citation used for the original source. I don't think providing a link is adequate at all times either, as that one article that goes viral in a sense could be the one that makes your blog gain that needed popularity for success. If everyone views your work on another site your blog doesn't get all of those valuable hits. All in all I don't know how this problem could be policed.