Bad:
I had lots of "stuff" as a kid that would be worth $$$ now. My grandfather gave me a baseball that was signed by Mickey Mantle and a few teamates. Years later I got the bright idea to retrace the signatures with a ballpoint pens since they were beginning to fade. Yup....RUINED any value it might have had
Worse:
We visited Fred Bear's shop when I was a kid tagging along with a buddy. Fred happen to notice the two youths admiring the bows. He came in, pulled two recurves off the line and signed them (with our names too!)
Years later in college I was desperate for cash and sold mine
Stupid is as stupid does