It's a good track record unless it happens to you, and then you're screwed if you didn't do something else to save it. I'm sure at least one person on HN has posted about losing all their data 'cause a machine failed.
It's the equivalent of not getting insurance. Yes, it saves you money, but on the other hand if you're really unlucky the consequences are truly dire.
http://aws.amazon.com/s3/#protecting
I am totally okay with 99.999999999% durability. This is way better than I'll be able to build/afford on my own.
In case of an epic S3 disaster, we could backup our S3 buckets to another offsite storage, but we're not going to improve much further than what their giving us.
It's the equivalent of not getting insurance. Yes, it saves you money, but on the other hand if you're really unlucky the consequences are truly dire.