Autograph hunting can be a deadly business...
I was responsible for two deaths in the Tolkien family, which led to the rumor that refusing an autograph request from me can be fatal. I had a copy of Smith of Wooten Major
that I thought I'd send to Tolkien for an autograph. This was in 1971. Months passed and I received the book back with a note from his agent saying that Mr. Tolkien was not signing anything right now because his wife had just passed away. I understood. So I waited a year or so, and then sent the book to him again. This time it came back with a note from his agent regretfully informing me that the book was being returned unsigned because Mr. Tolkien had, sadly, passed away.
Yikes! That's one book I'm wrapping in lead and never sending anywhere again.
Something similar happened to me and Rod Serling. I met him at a speech he gave at West Valley College in the 1973 or '74 (where I also first met Ray Bradbury, Buckminster Fuller, and Arthur C. Clarke!). I asked him for an autograph and he said in that great voice of his, "I'm sorry, I don't sign autographs."
A year or so later.... dead.
So it's unwise to refuse me an autograph or even to tarry in responding to the request....