Flickr has been around for a while now (in web-time). It's a great way to share photos and also have an online archive or backup in case something happens to your other offline backups. If you haven't made a backup plan and started to use it, it might pay to get on to that. If you don't you might well regret it.
One thing that I wasn't aware of myself until recently is the use of 'Guest Passes' for your Flickr account.
You might like to have it so that no one, not even registered users, can access your photos unless you specifically allow them to. However, by using Guest Passes, those people do not need to be registered with Flickr. This seems to me to be a great way to make it easy to give targeted access to your content without them having to sign-up to Flickr just to view it.