I can only speak for me and I have only cared about two celebrity autographs in my entire life (and gotten them) so I may not be the best qualified to speak to this but I'm going to.
Stephen King has been my favorite author since I was a child. His books have been there for me through cancer, through the abandonment of both my father and mother, through struggling through poverty, as well as every single great, wonderful, fantastic time in my life. I've always had his books to turn to, to share, to treasure.
When he has signed a book for me, it puts a piece of him into that thing that means so much to me. He wrote that thing I love so much, and the fact that he has signed it indicates that he and that beautiful thing that I own have shared the same space, even for an instant.
That probably sounds corny and sentimental but that's what it is. So I'm not ashamed of standing in line for an entire day to get that moment. And to be able to look back on that signature and know that this man who has given me so much shared the same space with me.
So. There. Enough emotion!