IS IT "verboten" or just "splitting hairs"? Technically, that's the issue between Howard Landau, of Hawthorne, N.J., and United Airlines. Mr. Landau says there was nothing wrong with other members of his family using United tickets bought in his name and that he was entitled to credit for them on United's Mileage Plus frequent flier program; United says that an individual "accumulates mileage in his account" -- their lingo -- only for miles he flies himself. We would guess that United has the better half of this argument over fine print, since it wrote the fine print in the first place.

But which of us doesn't sympathize with Mr. Landau? Here is a man who was thrown out of a club after his family accumulated 2 million miles worth of credit to get in. United may be right in saying that Mr. Landau broke its rules and is claiming credit for more miles than he is entitled to. But surely United is being shortsighted in ruling that Mr. Landau is not entitled to credit for the miles he is entitled to and cannot get credit for any more miles in the future.

Some may take all this as a flaw in free-market economics: a big company is happy to make you lots of promises, but if it gets too expensive -- Mr. Landau says he earned $150,000 of free air travel and bonuses -- the company will renege. We see it as an illustration that even in the most deregulated of markets not everyone will act rationally. Consider what Mr. Landau had to do to rack up his mileage: fly back and forth to the West Coast over the weekend, patronize United and Hertz and Budget rental cars and Westin hotels even if they were not what he wanted or could afford, fly across country stopping in Cleveland, Chicago, Denver and Salt Lake City in order to total up more segments. Anyone who thinks this is glamorous living hasn't taken the redeye or spent a few hours in O'Hare lately.

As for United, it hardly makes commercial sense to reward brand loyalty like Mr. Landau's with a kick in the pants. Frequent-flier plans work because people who travel a lot at their company's or clients' expense get direct and untaxed rewards for doing so; but if the ultrafrequent flier fears he will be suddenly cancelled as he is about to claim his 27-day cruise to the Orient, he is less likely to take a United flight with a Stapleton stopover than a competing airline's nonstop.

A good case can be made that frequent-flier premiums should be subject to income tax; that would make them less attractive and might lead to their demise. But so could "splitting hairs" and banning accumulation of additional miles by those unilaterally declared guilty of things "verboten." Mr. Landau has switched to American's "AAdvantage" program, but his lawsuit could jeopardize the existence of the frequent flier plans that he loves so much.