(ie - savvy enough to use/explore your site while not knowing about fb/flickr/etc)
Yes, indeed. I have a few friends who use fb and after some time they tend to think that "everyone is on the facebook". ;-) But actually not. There are many more people who don't know what fb is, or they don't use it.
My point wasn't that there aren't millions of internet users who aren't on facebook - it's that there aren't millions of internet users who WOULD BE INTERESTED IN SHARING PHOTOS who aren't on a social network of some sort..
How do you think most users of digital cameras share photos? via email? Print them out? You know, and I know those two methods are rubbish.
Even if there isn't millions of users - you'd only need a few thousand to get your startup rocking.
my mother and father both use online services (eg ebay) and have never heard of facebook - they've both rang me up and asked me how to share photos they took online.
(I told them to use the me.com services, fwiw -- that'll be a huge competitor to "mom and pop" photo services)
You said it yourself:
>But there are always people who are looking for a better solution.
Don't dive straight in, work out what users want that flickr/etc doesn't offer - and do that.