With Crashplan getting to be a bigger and bigger PITA to use in FreeNAS, this would be GREAT! I'll
throw money at Amazon if there were a way to use this via rsync.
EDIT - rsync so that you can store snapshots and have filesystem history - useful for backups, since a file that has recently been corrupted or accidentally damaged/spoiled by a user can be recovered with an earlier version. You can also send an encrypted stream to keep your files private.
EDIT2: OK, this is a bit off-putting:
"3.2 Usage Restrictions and Limits. The Service is offered in the United States. We may restrict access from other locations. There may be limits on the types of content you can store and share using the Service, such as file types we don't support, and on the number or type of devices you can use to access the Service. We may impose other restrictions on use of the Service.
"5.2 Suspension and Termination. Your rights under the Agreement will automatically terminate without notice if you fail to comply with its terms. We may terminate the Agreement or restrict, suspend or terminate your use of the Service at our discretion without notice at any time, including if we determine that your use violates the Agreement, is improper, substantially exceeds or differs from normal use by other users, or otherwise involves fraud or misuse of the Service or harms our interests or those of another user of the Service. If your Service Plan is restricted, suspended or terminated, you may be unable to access Your Files and you will not receive any refund of fees or any other compensation."
[Emphasis is mine]
So if they don't like the device you're using (a NAS instead of a phone or "normal" PC), or if they think your usage pattern is nor "normal" (which it won't be - a NAS backing up to this kind of service will definitely stand out), then they can just turn off the account and not refund your money.