In this case, the platform exists. This would be moving it to mobile and extending its audience/reach. I'm not big into photography so I'm a terrible judge of this particular domain. But it strikes me that if you are absent in such a large market as mobile, but already have a substantial user base you're risking losing customers as they move to the more convenient platforms. It also presents a barrier for new customers: go with a potentially better, but not on mobile, platform, or the slightly inferior, but available everywhere, platform?
