I've done several DietBets over the last few years and have everything found them hugely motivating. You don't have to pay the $5 for a membership fee, just remove it from your cart. If you want the highest payout, stick to games in the $30-35 range with the most players. Games that cost a lot to bet ($100+) have lots of winners because no one wants to lose that money, and the more people who win, the less money there is to split. Join the larger games that have over 1000 participants, and you'll lose some weight and make some money. You're not going to be making hundreds of dollars though...be realistic. The goal here is motivating yourself to be healthy, not making money. On average I've made an extra $20 or so in addition to my initial bet. If you're just looking for a way to make cash, this isn't it. It's about weight loss and health.
Bottom Line: Yes, I would recommend this to a friend