The reason I would want to sign up a photo sharing service is to be able to display them online and also have them backed up at the same time. I am notorious at the backing up part. Guarantee me these 2 things and I'll be your paying customer.
Edit: Right now I don't find the Ad Free account attractive, just saying. If anyone can have the same storage, what is flickr selling?
Backups are interesting, and something I had considered as a primary feature of the site. However this site is (currently) just me, and I don't feel that I could wholeheartedly say that a backup system relying on a single person is a good idea :) (unless that person is cperciva, in which case it's a-ok!)
Obviously I'm not expecting photos uploaded to the site to disappear at any moment (they're all on S3 anyway), but I'm not confident enough in the system yet to be able to offer anything like that, unfortunately.
It seems like not many services want to be the full RAW backup service that also does easy photo sharing. As in press a button and get a zip file of the gallery type of photo sharing that you get with G+. You do
You have 3 tiers:
1. RAW backups
2. Full JPEG renders downloadable in a zip file
3. Smaller JPEGs for online slideshows and viewing.
Edit: Right now I don't find the Ad Free account attractive, just saying. If anyone can have the same storage, what is flickr selling?