The key problem in this sort of site is being evidently and memorably distinct from the numerous other similar options, from email to facebook to flickr. I'd have to register with you to figure out how you're different/better, which isn't worth the effort because I'm not convinced there's some obvious problem with the way I share photos & links right now that you guys have solved, just because you "applied the family perspective" or whatever.

You have to attach to an emotional need people have regarding their families. Here's one I think many of the folks on HN share: guilt about not staying in touch with family members that live far away. One way you might tap into that need could be to offer a "time-release" delivery option, where I can seed my family account with a bunch of photots, and your service can send them out to my family at a rate of say 2 per week. I'd get credit for being in touch with my family on a regular basis, and each email can be a starting point for discussions and stories that bring us together around a particular memory. Plus, we're coming back to your site again and again over time, and I wouldn't mind paying a few bucks per month if you could send printed photos to my grandma who doesn't use email.