I appreciate that initially you need photos and maybe that is why the site is geared as it is, but what you really need to be testing is if you can sell the photos, will people come to you to buy them.
I'd assume the "cell phone generation" is a slightly younger mix, one person telling someone else that they managed to top up their phone credit this month from the money made from selling cell phone pictures is going to be all the advertising you need, could be very viral in that regard.
But marketing those photos to potential buyers is probably where the hard work begins, and in my opinion your site says nothing to point me in the direction of buying photos, what I could use them for etc. iStockPhoto, Getty Images and the like don't target photographers on their homepage, they target people who use photos and you need to do that to.
Awesome idea though, I really like it, I can really see how you can make money from it and how people might find it useful. Being able to geotag and search against that would be amazing too - concerts, riots, natural disasters etc etc. Good luck. (Future feature, let Twitter trends create a list of "Photos we need now" so that when photographers come to your site they know what bloggers might be looking for).