Hi Mark - sorry for the delay!
It's great that you show interest in how we administer GMC
When we had our first "guest" instructors way back I used to create a new topic for every lesson (like Nick said) - however that would be hard for me to do now... Instead I try to get to commenting all lessons. As opposed to most other video sites content presented on GMC is all "editorial" - which is why I think it's important that someone administrating the site shows his/her presence in the content presented.