Everybody loves free stuff, which is one reason the average American household participates in a whopping 18 consumer rewards programs. But while more companies are offering points, miles and cash-back rewards than ever, that doesn’t necessarily mean each of those 18 is worth a spot in your wallet.
No one tracks exactly how many companies offer such loyalty programs, where customers get discounts or bonuses for shopping often, but experts agree they are multiplying. Once primarily the domain of the airlines, now....