Don't Blurt Out the Answer!

With the markets and economy in the toilet, we are amusing ourselves at work doing puzzles.

Here is the latest one. Can you guess?

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?