I wouldn't underestimate what people might respond to. A few years ago if you told me a photosharing app that deleted the image you shared after 5 seconds would refuse 2 buyout offers in the billion dollar range then I'd call you crazy :)
You need users doing what most of them are not comfortable with. Photosharing is ok for everyone i guess. But if you will make app in which everyone draw on phone like Picasso it would be different story :)