Set per-file size limit per blog?

Does anyone know of a plugin, or a method, used to set the per-file size limit on individual blogs?

I run a Multi-Site install, and I want to limit most of my users’ file sizes to under 1MB – I have way too many users who don’t properly format images, and upload 8MB files. On the other hand, I have groups of users who need to upload larger file sizes (audio and/or video), and they understand web formatting, etc.

I would like to be able to, by default, set the per-file limit to 1MB and also be able to change the limit for some blogs that require larger file uploads.

Any suggestions? I’ve been searching a bit, and haven’t found anything useful yet…