A long time ago we opened a JetBlue forum because their group came to us asking for this help. These forums had about 200 registered members when that happened; a blip compared to every other pilot forums' traffic.
Today is a bit different. If we opened up a separate forum for FedEx and UPS, then we'd also be obligated to open one for Continental, Southwest, ExpressJet, and others that have lots of pilot posts pertaining to that carrier.
I believe that having a lot of FedEx and UPS posts in the cargo forum isn't a problem. There are almost 7,500 pilots between them, so their posts will of course outnumber those coming from airlines like Gemini and World.
We're always looking for ways to tweak the forums to make a better user experience, so --as always-- thanks for the feedback.