Yeah, it happens to me too. Recently I rented the "Phantom of the Opera" DVD, it was one of the most horrible experiences I have endured, but still, I couldn't turn it off, I had to watch it till the end. I don't know, maybe it's curiosity, I just need to know how it ends. It happens to me with forums too, once i'm obsessed with one I have to read every single thread, every post... it destroys my productivity... 
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"Whatever you do in life will be insignificant but it's very important that you do it because no one else will."