Retailers that get the most payback from loyalty programs are careful to measure vital metrics, like gross margin per customer and the lifetime value of a customer, which is tracked by using surveys and following forwarded emails to see who's recommending your store.

FORBES: Loyalty Programs Lose Points With Shoppers

Here, CAC is cost of customer acquisition, MRR is monthly recurring revenue and software margin is the cash they keep for each customer after accounting for support and other costs.

FORBES: In Defense Of The Lifetime Value (LTV) Formula

In addition to generating its heaviest customer activity in lower-margin prepaid calling plans rather than in the more lucrative post-pay multiyear plans, RadioShack's wireless business is being sabotaged to a degree by its own partner.

FORBES: RadioShack's Quick Fix

The industry was super competitive, and service providers were looking ways to improve customer loyalty and use of higher-margin data plans.

FORBES: Apple TV: Big Potential in 2013

Their plan was to sell low-margin baby goods with maximum customer service: Moms could place an order once and renew it on a regular basis, often with free overnight shipping.

FORBES: Amazon Wraps Up Diapers.com for $540 Million

Plus, a margin umbrella now exists for competition that chooses to undercut your margin model with a more efficient customer acquisition strategy (such as giving the customer the money).

FORBES: The Dangerous Seduction of the Lifetime Value (LTV) Formula

Compare that margin with what you make on the average customer.

FORBES: Calculating The Economics Of Loyalty

Now here's Wall Street's dirty secret: Brokerage firms are free to lend out any shares that customers put in margin accounts, the kind of account that allows the customer to borrow against his securities.

FORBES: Shortchanged

H-P said Tuesday that Autonomy, before it was acquired, had mischaracterized some sales of low-margin hardware as software and had recognized some deals with partners as revenue, even when a customer never bought the product.

WSJ: H-P Blames $8.8 Billion Charge on Bad Deal