A brief word on FSLR's core technology is in order. First Solar has the distinction of being the first solar (okay, pun intended) manufacturer to produce solar panels at a cost of $1/watt. The key to their success has been the use of cadmium-telluride. The price of cadmium has been deregulated since the 1950s, its worldwide supply sources are geographically diverse, and there is a growing market for recycling cadmium in the U.S. Tellurium, although not a rare earth element, is so rare in geological availability that the U.S. government has difficulty estimating its worldwide production. If resource availability will ever constrain First Solar's ambitions, falling tellurium supply will be the main culprit. Tellurium is largely a byproduct of copper mining and the world price of "Dr. Copper" has fallen this year in response to slackening world demand. The long-term outlook for tellurium is not rosy, as Jack Lifton has noted in this article addressing FSLR's ambitions. No matter how compelling a value FSLR may appear based upon financial reports, the realities of geology will govern its future.
Full disclosure: No position in FSLR at this time.