Amazon Prime is now offering unlimited cloud storage for Prime Members in a program called Amazon Cloud Drive. This is on top of their 2 day free shipping, Amazon Instant Streaming Video and their Kindle lending library.
It's also a clever ploy to make sure people keep Prime even when prices increase. If you have backed up all your photos with them, you are probably going to want to stay with them.
I don't have Prime (other than a 30 day trial) and I don't plan on getting it for this reason, but it is a good benefit to have and some people might be interested in signing up.
Not a prime member? You can get an Amazon Prime 30 Day Trial for free to see if you like it.