This could be indicative of a newer iPhone version in the works. Apple wouldn't really want to replenish stocks with an "old" device and then bring out a new one with tons of leftovers of the old, no one would want them except at a severely discounted price. I'll check my local Apple store and see what they have in stock.
funny i was at the Apple store in stamford yesterday and they were indeed out of stock...i didn't bother asking why or anything i just overheard the manager telling some lady that they get new shipments in everyday and they might/might not get more iPhones in depending on what Apple sends them on that particular day. just my $0.02
Best Buy does NOT sell the iPhone, period end of story. iPod touch, yes iPhone no.
And actually they are becoming more scarce at Apple stores. I was in the Knox store here in Dallas a few days ago and they had a couple each of the 8 and 16GB in stock the lady I spoke to said they have been running out from time to time. They still get frequent shipments almost daily but seem to get less of them than they were getting. Really it only makes sense, its the typical life cycle of a tech product. The iPhone has been out almost 10 months now. New product rumored to be out. Demand dwindles for old unit in anticipation of new device. Production and shipments of old device decrease. Not really any big news here.