Where have all the 8GB iPhones gone?

Inventory numbers on the 8GB iPhones are extremely low according to retail sources (via AppleInsider). Now what do you think could be causing this shortage?

Apple often tries to clear out their inventories before launching new products, or upgrades. So, why would Apple let the 8GB model run dry when they only have 8GB and 16GB models to choose from? Either there’s really just a shortage of this model, or Apple is likely prepping for a larger capacity iPhone.