What Am I Riddles

Question: I dig out tiny caves, and store gold and silver in them. I also build bridges of silver and make crowns of gold. They are the smallest you could imagine. Sooner or later everybody needs my help, yet many people are afraid to let me help them. Who am I?

Question: I'll amuse you for an entire evening, But you won't remember me. What am I?

Question: What is bought by the yard by is worn by the foot?

Question: What flies when it's born, lies when it's alive, and runs when it's dead?

Question: If you have me, you want to share me. If you share me, you haven't got me. What am I?