As the US dollar continues to be devauled the metal content value of US coins will eventually be worth more than the face value of the coins.
There use to be silver in US coins but due to the continued debasement of the dollar, the silver content of the coins became more valuable then the face value of the coin. People could melt the coins into silver, sell the silver and be better off.
There use to be copper in US pennies but the copper value of the coin increased over the face value of the coin. Now a penny is mostly zinc.
This is an effect of Gresham's Law: "Bad money drives out good money."
Right now the metal content of nickels is worth more than their face value (Here is a neat website detailing the metal value of coins). I expect the mint to change the metal content of nickels to mainly be zinc instead of copper. This will make pre-2010 nickels dissappear from the market since people would rather hoard copper nickels and spend the less valuable (in terms of metal) zinc nickel.
Do you think it is worth the hassle to stockpile nickels?
NOTE: I'm not suggesting that I melt the coins. I'm just suggesting that I hold onto the nickels and sell them later when they are worth more than 5 cents. For example, you can sell coins with silver in them for far above their face value.