Some sort of premium paid membership for extra access/privileges? Maybe how-to videos or a mail-order DVD? Limit the amount of certain functions to non-paid m

Some sort of premium paid membership for extra access/privileges? Maybe how-to videos or a mail-order DVD? Limit the amount of certain functions to non-paid members. They are only allowed X type actions per day/week/month etc. I also had a Groupon like idea, but not sure how you would implement that. For instance, if several friends are doing a weight-loss challenge, if they collectively lose Y lbs within a specific time period, something is unlocked or given. Maybe make this a premium-only membership. You could also have page for healthy foods/supplements that link to amazon's affiliate program.