I think one of the most interesting parts of this is how they plan to ensure that people do not use it for transient backup: https://aws.amazon.com/glacier/faqs/#How_am_I_charged_for_de...
Deleting data from Amazon Glacier is free if the archive being deleted has been stored for three months or longer. If an archive is deleted within three months of being uploaded, you will be charged an early deletion fee. In the US East (Northern Virginia) Region, you would be charged a prorated early deletion fee of $0.03 per gigabyte deleted within three months.