AT&T yesterday reported robust early sales for the iPhone -- but not robust enough. Investors expected more, and the price of Apple stock dropped as a result. But the figures represent a single datapoint, with no bearing on the long-term outlook for the iPhone.

AT&T, the exclusive service provider for the iPhone, reported on Tuesday that it activated 146,000 iPhones in the quarter ending June 30. That kind of sellthrough is great - but not good enough. Apple stock slumped, because analysts were expecting much higher; Goldman Sachs estimated sales of 700,000 units that weekend.

The AT&T report obviously isn't good news for Apple, its investors, partners, and enthusiasts. But it's not bad news, either. It's just information. It says absolutely nothing about whether the iPhone is going to be as revolutionary as Apple hopes.

Here are some reasons why the AT&T reports don't mean much:

• AT&T isn't even reporting on the full weekend of sales. The iPhone went on sale Friday at 6 pm; AT&T's reporting period ran through the following day.

• AT&T stores ran out of stock as early as Friday. I can testify to that personally;. You can't sell what you don't have.

• People reported problems activating the iPhone through AT&T in the first couple of days. And AT&T reported its total sales figures based on the number of iPhones activated, not on hardware sales.

• The expectations for that weekend were outrageously high.

Piper Jaffrey analyst Eugene Munster told the New York Times that iPhone sales "were largely in line with analysts' earliest targets, but as public excitement grew, so did investor expectations." He noted that the iPod was considered a disappointment in its first quarter on the market in late 2004. He expects similar, gradual growth for the iPhone, with a surge in 2009.

Again, I can back this up based on my own anecdotal experience. When I show the iPhone to friends and family, they look it over, press the buttons, hand it back to me, nod decisively and say they're looking forward to getting one - around Christmas. Or in a year. When the bugs get shaken out, a couple of new features get added, and the price comes down. This is hardly an unusual buying cycle for gadgets.

We'll know a lot more about early iPhone sales in a couple of hours, when Apple reports its own results for the quarter. Watch InformationWeek; we'll bring you that news as soon as it happens.