This is kind of amazing when you think about it. According to Macworld UK - reporting on information from DRAMeXchange - Apple has secured about 25% of the entire world's supply of flash memory. That's a lot of iPod nanos and iPhones!
Apparently, production problems have reduced yields, leading to increased flash prices and even shortages for other vendors. When you consider all the memory cards for cameras, etc. out there, that Apple is using that much of the global supply is quite remarkable.