It looks like that hard limit became a soft limit in August:
https://aws.amazon.com/about-aws/whats-new/2015/08/amazon-s3...
Hmm... I didn't know this. The last time I asked they said it would never happen. I was told the original reason was that all buckets had to have a unique name
The reason is so if you fuck up a scaling script for example you can't launch 1000 machines and take all the capacity and then bitch that you won't pay for it.
It's a stop gap.
However, aside from the hard limit of 100 S3 buckets, all other limits are configurable at the request of your AWS rep