Flickr is an image hosting service which is used to backup photos & videos online. Flickr allows other people to add your photos to their gallery. If someone adds your photo to a gallery, you will get an email notification. If you don't like that another member is using your photo in their gallery, then you can easily remove it. To remove your photo, click [X] icon located next to your photo in their gallery. There is another way to remove it. When you get a message about someone is using your photo in "Recent Activity", then click 'Remove it' link to remove your photo from their gallery.
You can install PicBackMan's Flickr uploader for Mac from the website and start backing up photos and videos.