do all the people using these kinds of paid services just have really tiny hard drives
Some tarsnap users back up all of their data; others just back up a subset. I'm not sure why you say that snapshotting isn't important -- in addition to the savings in bandwidth and storage, it makes tarsnap much faster and more convenient.
if the tarsnap server ever goes away, customers risk losing their data, since the server maintains the mapping of S3 objects to blobs
If the tarsnap server dies, I can launch a replacement EC2 instance and regenerate the metadata (as described in the article). If you're concerned about the possibility of me going away... well, if I get hit by a bus the tarsnap server will keep running on its own for at least the immediate future, but I have to concede that at the moment tarsnap won't survive indefinitely without me.
But I do my best to make sure that I won't get hit by a bus. :-)
Some tarsnap users back up all of their data; others just back up a subset. I'm not sure why you say that snapshotting isn't important -- in addition to the savings in bandwidth and storage, it makes tarsnap much faster and more convenient.
if the tarsnap server ever goes away, customers risk losing their data, since the server maintains the mapping of S3 objects to blobs
If the tarsnap server dies, I can launch a replacement EC2 instance and regenerate the metadata (as described in the article). If you're concerned about the possibility of me going away... well, if I get hit by a bus the tarsnap server will keep running on its own for at least the immediate future, but I have to concede that at the moment tarsnap won't survive indefinitely without me.
But I do my best to make sure that I won't get hit by a bus. :-)