How to I limit media file uploads for membership site subscribers?

I'm making a membership site, http://www.supportyouridea.com, where subscribers will be given their own page. I'm using the directory format so the subscriber url will be http://www.supportyouridea.com/username.

How can I limit the amount of user media files so I don't get hammered on bandwidth and the site doesn't slow down? I can have them use YouTube for videos. I wouldn't mind hosting one video for them if it was no longer than a minute. However, for easy user integration, photo uploads should be made using the media tab on the dashboard of their site so they can edit them and make a gallery much easier.

This site is designed for people who aren't that tech savvy and probably haven't heard of services like Amazon S3.

How is it possible to set a limit on the amount of media files one user can upload?

Thank you.