I have been a Flickr user since 2005. I have more than 18,000 photos stored there. Every photo, every scanned document and even screenshots are automatically backed up to Flickr. I control who can see my photos and which remain private. I can easily share my photos both within Flickr (Flickr Groups are awesome!) or to Facebook, WordPress, Tumblr and by mail or message. At $50/year it is not only a fabulous backup service, it’s also a gorgeous platform to display my photos.
If that’s not enough . . . all my photos (except the ones I’ve set as private) are very searchable and have attracted a number of research cousins.