An idea (from wordpress):

Create a plugin that allows admin to use Amazon's Simple Storage Service to host media for b2evolution.

Amazon S3 is a cheap and cost effective way to scale your site to easily handle large spikes in traffic without having to go through the expense of setting up the infrastructure for a content delivery network.

features:
- File uploads are automatically saved into Amazon S3 bucket
- files will be delivered by Amazon S3, instead of web host.
- "Amazon S3" tab next toregular "Upload" tab, allows to easily browse and manage files that were not upload via b2evolution