Last month, AAPL was around $200/share. In today's aftermarket, it's around $137 due to today's earnings call.
Although the drop, over the past month, was precipitated by the slowing economy. Today's drop was due to the fact that the iPod's year-over-year growth is approaching 0%; it was not due to Apple's conservative guidance for the next quarter.
Now, don't get me wrong. Apple's revenues will continue to grow and they could even surpass Microsoft's revenues in the next couple years, but iPod growth, in terms of absolute numbers, can't continue forever.