At long last, Apple is listed as one of the available brands of camera in the flickr Camera Finder.
This means that you can search for shots taken not only with iPhone, but with the three models of Apple’s original camera line, the QuickTake (codenamed Venus, Mars, and Neptune). Currently, there are no viewable uploaded photos taken with the QuickTake 100 or 150, but there are some from the QuickTake 200.
Update: A potential reason for the iPhone’s relatively paltry numbers is that when you email photos from the phone, it strips the exif data out which means those photos aren’t counted. I imagine many more people email photos to Flickr from the iPhone than upload them from their computers.