I couldn't pass up this exchange, from Randy Cohen's "The Ethicist" feature appearing in today's New York Times  Magazine.

Is it ethical for a cabdriver to charge more for a ride during a snowstorm? The cabs that operate out of my busy train station have no meters; passengers are normally charged a set amount per person based on distance from the station. What few buses there are don't run past 8 p.m., so unless you have a car or have arranged a pickup, the only way home is by taxi. Anonymous, Woodbridge, N.J.

It is not unethical for cabdrivers to charge whatever passengers are willing to pay -- an amiable word, ''willing'' -- but it can produce unfortunate results. It is called supply and demand, and you're seeing it in the form its partisans find most romantic: an unregulated marketplace. From that perspective, what you experienced is not only ethical; it is ideal -- free people making free choices freely (except for the inability to get home without big bucks or cross-country skis).

In a free market, increased demand for cabs on stormy days inspires drivers to flock to the station for a crack at those higher fares you mentioned. An increased supply of cabs causes fares to fall until equilibrium is achieved...

We cannot solve your cab problem or ours by relying on the altruism of individual drivers. Why should they be more self-sacrificing than Tiger Woods or Tom Cruise or Bill Gates? But we can create laws that promote the public good. In this, ethics expresses itself as social policy.

Woodbridge, however, chooses not to regulate fares. Cabs may charge whatever fare they like, provided they post it on the rate card and do not exeed that registered rate (which in some cases includes a $10 inclement-weather surcharge).