Along the same lines, there are some programming contests that use a web based system for submitting solutions. They often restrict internet access to just the contest website, but a motivated user could use the same trick with the user profile fields to sneak information in/out.
As a bonus one of those contest systems allows users to upload a profile photo, which would greatly increase the bandwidth!
As a bonus one of those contest systems allows users to upload a profile photo, which would greatly increase the bandwidth!