I responded to a PM about this, but I'll post here too. The back of my Chilli's bonus card says this:
"Present this bonus card for $5.00 off of your food and drink purchase at any participating Chilli's, Romano's Macaroni Grill, On the Border Mexican Grill and Cantina, or Maggiano's Little Italy restaurant in the US. THIS BONUS CARD IS VALID BETWEEN January 1, 2007 - February 28, 2007. THE BONUS CARD EXPIRES ON FEBRUARY 28, 2007. Multiple bonus cards can be used on the same check. LIMIT ONE (1) BONUS CARD FOR EACH $25 DOLLARS IN FOOD AND DRINK PURCHASED PER VISIT. The bonus card may be used only one (1) time and applied to only one (1) check. The bonus card is good for up to $5.00 off any meal at a participating restaurant but excludes alcohol and gratuity. The bonus card is not valid in combination with any other discount or offer. Recipient is responsible for any applicable taxes and fees associated with any restaurant visit. Bonus card may not be exchanged for cash, sold, transferred or reproduced and must be presented and relinquished at time of redemption. Any unauthorized reproduction, sale or transfer constitutes fraud. Void if lost or stolen."
At first it sounds as if you can use multiple bonus cards per visit, but then I think what it really means is that for every $25 of your check (not counting alcohol), another bonus card can be used. For example, if my table spent $100 on Chilli's food, I could use 4 bonus cards towards the total. That really means you can't go for a free dinner by using 5 cards at once and paying your whole bill with the bonus cards.