Definitely go with hosted. Every account you force people to sign up for will drop your user base by a ton. Would you be posting on Hacker News if you also ha

Definitely go with hosted. Every account you force people to sign up for will drop your user base by a ton. Would you be posting on Hacker News if you also had to sign up for S3 (or give your current S3 account) in order to provide storage for the comments? In addition, storing their S3 credentials has all its own problems. Remember that the AWS credentials are pretty powerful. If your database is compromised, those keys could be used to drain peoples' bank accounts via Flexible Payment System (FPS). Handle AWS credentials as you would a credit card number, which means avoid at all costs!