Another downside to your app is that it's on the iPhone platform, and I use Blackberry. If you had a way for me to use a normal digital camera with my PC it would help get me on board. There was some other new service here on HN recently that was called 'Sold' for selling stuff but it only worked on a certain platform I didn't have a device for, too- so I guess its not uncommon for startups to exclude whole market se…
To come to that decision, it was probably a factor of what you know and also some insight into the customer base. For example, maybe iOS users tend to be more likely to pay a premium for convenience or that in San Francisco, iOS penetration is higher than Android, etc etc.
If the product picks up traction, I will bet that their next move is to port to Android, then web, then maybe ... maybe windows phone and blackberry.