An office app over the net is one thing, I mean we all have bags of processing and bandiwdth going unused for such a mundane task.
But a photo manipulation app means
cpu cycles, memory and scratch files, something not well suited to being a remote app. Now if we're talking about basic cropping etc.. for sticking a photo up on the net quickly, yeah sure it might be handy, but I don't see even novices giving up locally run photo apps for a while yet.
That is unless all the processing is done there side at a speed competative with a well specced system, in which case it would be a great tool for those wishing to do resource intensive manipulation from any location regardless of the spec of the system they are using.
But how cost effective can they provide both an application and system resources?