I am participating in Microsoft Rewards. I can answer some questions if you have any.
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The concept: You earn points and use them to enter on sweepstakes, redeem them for a gift card, or donate to charity. You can not cash out on them though..
You earn points by searching on Bing, completing trivia quizzes (no personal info!), and using Edge. of course, the quizzes take place on Bing, so you can earn both at once.
Currently there is no referral program ;(