Leveraging social media on mobile devices is a task best saved for the established companies and the proliferation of the mobile applications, or at least that is the conventional wisdom. And while folks are waiting for Facebook’s photo-sharing application for the iPhone, the Instagram application as quietly grown to the tune of 5 million users who are all about sharing images with what some, including Lee Oden, have called a “Twitter for photos” service.

Considering the proliferation of Instagram, will Facebook’s photo-sharing app make as much headway as some expect? Will people, just because a new application has Facebook’s shiny logo on it, eschew the fun they are having with Instagram to embrace another service? Time will tell, but in the interim, Instagram will simply continue enjoying the incredible success its having.

Instagram’s success story had a light shined on it with a revealing article in TwinCities.com. In it, the numbers come into focus. 5 million users with over 100 million images uploaded, and while the service’s filter and other capabilities are acknowledged, it’s the ability to share these photos that helped make Instagram such a success story:

Local Instagram users interviewed for this article said, again and again, that picture sharing is a primary reason they have become so addicted. They can “like” their pals’ pictures and add their comments to the shots anywhere and anytime via the phone app, while posting their own shots to keep the visual conversation going.

Once you include the hashtag capability, giving such an index of images a level of categorization, the appeal is easy to understand. Of course, maybe people just like taking and posting pictures of their feet, and Instagram provides them with the easiest way to do so, or at least a willing community with which to share these images.

Another aspect of Instagram’s appeal also comes from the distinct lack of size of the company that developed the application. Allow some Twitter users to expand:

You mean not relying on hyperbole and letting the product speak for itself is a successful marketing tool? Who knew? Of course, the reason for Instagram’s incredible popularity may be something a lot more simpler than we realize:

“Cause it’s 1-8-7 on an unwanted app…”

Silliness with Snoop Dog aside, Instagram’s success is impossible to ignore. So much, in fact, that a video interview with CEO Kevin Systrom, courtesy of GigaOM TV, was featured on Reuters:

Haven’t seen an application developer celebrated like that since Angry Birds, which brings us back to Facebook’s upcoming photo-sharing application. Considering the success of Instagram, will it be too little, too late? Will current Instagram users want to make the switch from the service they are comfortable with just use another application that shares images? Let us know what you think.