Does MageRewards have fraud protection?
With MageRewards we've tried hard to give a lot of power to the merchants. Depending on how merchants wish to setup their rewards campaign, there's a series of security measures they can take. For instance, all points earned on an order can initially be in pending status until an invoice or shipment has been made on the order. Other types of earning can be setup to start off in pending status until an administrator approves them.
With specific cases, like signups, if merchants chose to actually award someone for signing up to the site, we advise the awarded points here to be less than a minimum redeemable amount in the store. Of course customers can't signup twice but they can send points to another friend. This feature can be disabled from the admin panel especially for stores that award a lot of points for reasons other than order completion.
With other cases, like Facebook Like on products, we've implemented a hold functionality and a maximum number of points awarded for like actions. With this, MageRewards will check back to make sure the "Like" is still there after a configurable interval before awarding points.
Other features like leaving reviews, tagging products, referring friends, all have their own configurations which allow merchants to keep a closer eye on who's getting their points approved.