From the article:
You’re watching your favorite TV show and there’s a one-minute segment that is especially good. You record it, throw it up on YouTube and then write a lengthy blog post about it. Not only are you hyping up the great episode, but offering lots of commentary on the show and that particular portion of it. You’re not making any money from your site and, truth be told, the clip is only a small part of the post, down at the footer even, but it all goes together very well and creates a nice review of the episode and the segment.
Yet, despite all of this attention to making your use of the video as fair as possible, two days later the video stops working, the owner of the content filed a DMCA notice and got the content removed. You could file a counter-notice, but after 10-14 business days, the post will be long forgotten.
What has happened? Although your post is "transformative" within the meaning of copyright law, the video itself, hosted at YouTube without your commentary, is not - and that's where the copyright holder sees the video and makes any assumptions he or she needs to about the legality of the clip. And what's worse, given YouTube's business model, this can't be changed.
Read the article at the Plagiarism Today blogsite here.