Stedsm,

This cannot be a "review" campaign.

You must pay a definite momentary benefit for the reviews hence what you will be crediting people do not need to be the actual money (it can be a play-money). For the reviews you must pay a definite reward as you enroll people based on forum rank and not just in random.

Just my opinion; people who prefer enjoying new sites and not minding their time/efforts for reviewing may not bother this.