If you are looking for cheap online backup storage for photos and you don't need the other marketing tools of photoshelter etc. you should check out JungleDisk at http://www.jungledisk.com

It uses the Amazon S3 service to offer online storage where you only pay for what you use, and it mounts as a drive on your Mac.

I have no affiliation to JungleDisk, but it seems a good service.

Dave