I'm new to the site and think this is an awesome tool to help people lose weight. My suggestion is to have a Forum section dedicated to Weekly weigh-ins where people can post on one specific thread or a thread of their own their weight and/or measurements weekly (I noticed that someone started a thread in one of the other discussion forums like this). I have found it very beneficial to have a specific day that I check my weight per week. This may help people to stay accountable if others can check on their progress. But it won't clutter up other discussion forums.
Let me know what you think.