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In other words, the system is far from transparent, and customers ultimately lose out, according to Tim Winship, contributing editor for Frequent Flyer magazine. "The airlines are worried about squeezing every last possible penny out of the demand out there," Winship says. "They don't want to displace a revenue passenger with a rewards passenger."

2. Watch out for other tricks

Another common complaint among business travelers is that airlines change the rules in mid-game, sometimes moving the finish line for an award. Whereas 25,000 miles may have been enough to land you a domestic, round trip restricted coach award--the de facto industry standard--you may end up racking up tens of thousands of more miles before a seat actually becomes available. Or you may encounter a reservationist who "suggests" you double the amount of miles for the frequent flyer seat to 50,000 and--bingo--the previously unavailable frequent flyer seat becomes available.

Certain travel agencies, such as Award Planner promise to find you a booking using your miles--often for flights that you've been told have no availability for reward tickets (they know all the tricks apparantly). But for this service they charge a fee of $39.95; $99.95 for an annual membership.

Another zinger: rush charges, slapped on for making reservations too late. These can range anywhere from $25 to $75, depending how far in advance of your departure date you book.

And there are other fees. Air Canada, for example, now charges passengers $25 Canadian per award ticket, if not purchased through its website. A few years ago, the same ticket would have, with miles, been totally free.

Regular business travelers are starting to notice, and lose faith.

"They make it impossible to travel anyplace desirable other than during monsoon season," says Jessica Wollman, a producer with Scholastic who flies about twice a month. "I usually hoard my miles and entertain fantasies of trips to tropical islands but end up using them for practical stuff, to get to weddings and job interviews."

3. At the end of the day, airlines win

Many people think that the way airlines make money is by "breakage," that is, by failing to redeem their miles for awards (more on this later). They don't. Their partnerships are the real profit-centers.

Take American, for example, which has the most participants, at 45 million (a somewhat disingenuous number; it includes every person who has ever signed up, living or dead, according to Winship of Frequent Flyer).

American boasts 1,500 partners, especially among hotels and rental-car companies. For every mile they award, the partner must pay American Airlines about two cents. It almost goes without saying that this adds up to hundreds of millions in revenue a year.