Molycorp (MCP) is having a tough time as prices of rare earth metals tumble. But it's good news for consumers and tech hardware firms. Rare earth metals are mainly used to make powerful, tiny magnets for everything from electronic devices like MP3 players to batteries in electric cars from Ford (F)and GM (GM). They also go into the tablets and smartphones made by Apple (AAPL) and Samsung, and PCs and notebooks made by Hewlett-Packard (HPQ) and