That would essentially just merge the video clips and TV / Movies into one forum. I have suggested that before:
http://www.sythe.org/denied-suggestions/986002-off-topic-forum-revisits.html and it was turned down because of the inherit differences in the forums and the fact that they were both at least someone active.
I addressed that in my OP but I can give the long version. It is abundantly clear that adding subsections for topics does nothing to increase the discussion of that topic unless there was so much preexisting activity that it became hard for users to filter out the threads for that topic from threads about other topics in some more general forum. The idea that adding forums for specific topics to encourage posts about that topic has been tried over and over again and has not generally worked. Look at the sports section which has been added and removed multiple times and although it has had great amounts of support, it has never been extremely active.
Why is the case? Well without very specific log data and A/B testing it is impossible to truly know. However with a bit of thought I believe we can figure it out. Users are not going to spend all that much time on Sythe unless there is content they wish to consume and discuss. Web users have very short attention spans which is why things such as bounce rate matter as much as they do. Uers are going to click on forums that they believe have content that they wish to see. If a section is active there will be a lot of content that they will want to view and they will stay on Sythe for a longer amount of time. In addition, since they found the content they wanted to it is going to condition them to return to that specific forum in the future. If they click on a forum that interests them but is inactive and has very little new or relevant content, they may still be satisfied with their visit. However, if they return and no new content is there, it is likely that they will be put off and conditioned to not visit that specific forum again.
In addition, it is likely that users will only click on forums that they already feel like they will like and it is less likely that they will click on a forum that they do not already feel like they will like. By merging two similar forums, the user will see more content that they would have otherwise not seen with the added benefit of it being content that is similar to content they already like.
By merging the sections you get more activity out of that section because there are more threads and more topics that are relevant to that section. However, you also get the added benefit of exposing users that like similar content to content they would not have otherwise seen which increases the likelihood of them adding their own content. Merging the forums also reduces the number of clicks that users have to do in order to get the content they want in front of them. If they click on a few forums that they want to see content for and all of them have no new content for them they are likely to get dissuaded from clicking on the next forum that may have new content that they would have otherwise enjoyed.
Obviously if a section is too active, it becomes hard for users to find the content that they are interested in. In this case this would drive overall activity down since users would find less content they would contribute to. This is when subforums are optimal so that users can more easily find the content that they want. With sections that combined only would have only a handful or two of threads that were posted on in a day it is unlikely that a user would miss any content that they would have liked to contribute to.
