I think the underlying meaning is pretty obvious. For a photography "purist", of course there's no way the iPhone (or any other smartphone or P&S) is going to be enough. They don't match up to a DSLR or MF/LF camera on many levels. For somebody who puts tons of thought and effort into every image they take and insists on top-flight image quality, such a camera is no solution for them. OTOH, there are many, many more people in the world who simply use their cameras for snapshots of their friends to post on social networking sites or just to have some memories of their vacations, families, etc., and don't insist on every picture being technically perfect. No way they're going to lug around a shoulder bag/backpack with 5 lenses, two bodies, flashes, reflectors, a tripod and all the other paraphernalia everywhere they go, nor are they going to shoot raw format and spend time downloading and post-processing on their computers - they just want to point their camera at something or somebody, push the button and immediately post it or send it off in an e-mail or SMS. They're not interested in the MTF charts for their lenses, lp/mm resolution, bokeh quality or any of the other technicalities that "purist" photographers obsess over. For those people, a smartphone camera is the ideal solution. If Annie Leibovitz' "friends" are mostly casual photographers who aren't interested in putting forth the time and effort to learn how to use a DSLR to its potential, then I'd say she's right on the mark. I doubt she was directing her comment toward "serious" photographers.
I have an iPhone. It's with me everywhere I go and I take a lot of pictures with it, with a full understanding of its inherent limitations. I also have a decent DSLR kit. It's not with me everywhere I go and I only bring it along when I intend to do some sort of "serious" photography. Wanna guess which one I take more pictures with? Not saying they're better or even as good, but any picture is usually better than no picture when you spontaneously run across something you really want to capture.
I think we (collectively) on these type of forums sometimes lose sight of the fact that not everybody in the world is as "serious" about their photography. "Hardcore Photography Enthusiast" is a very small subset of "People Who Use Cameras to Take Pictures".