I have to admit: this is a little surprising at first glance. AT&T is reporting only 146,000 iPhone activations "in the first few days of its availability," which has led to a downturn in Apple's share price today (as of this writing it's down over 8 points to about $135). AT&T's share price is also down, despite the carrier reporting 61% growth in profits in the second quarter.
Apparently, what happened is that analysts built up wild and unrealistic expectations for the iPhone launch, and with the numbers looking a bit softer than expected, the stocks are taking a hit. I think it's really much to early to say anything definite, with the 146,000 activations only covering a vague "first few days." It's still going to be a while before we know the full extent of the iPhone's market penetration, and it's certainly much too early to jump ship like so many of these skittish investors and analysts.