From today's herald tribune: (www.iht.com)

I am 6 feet, 2 inches (188 centimeters) tall with a back problem and cramped seats in economy give me a lot of pain. So I was fascinated by your suggestion to buy two or three economy seats as an alternative to an expensive business-class fare (March 22). But do only British Airways and Delta accept such bookings?

I called Virgin Atlantic and Continental Airlines, which confirmed that they allow bookings of multiple seats for this purpose ("As many seats as you like," a Continental spokesman said.) But, as I pointed out, you must make sure that your seats are pre-assigned - and together. I did hear of a wide-bodied traveler (a true story) who found to his immense chagrin when he boarded that the two seats he had reserved for himself were on either side of the aisle!
.
Carol Fitzpatrick in Hartford, Connecticut, strikes a cautionary note: "While it is standard industry procedure to sell extra seats to people with special needs, it is important to make sure that the assigned equipment for all flights has armrests that are not fixed in the down position." She warns that "specific airline seat assignments are never guaranteed for anyone, period." And that "airline personnel, and computers, often reassign seats. Many families with adjacent seating prearranged have found themselves split up because of such an occurrence. Or, you'll find a 'platinum executive' frequent flier who has been accommodated in one of your seats."
.
In such cases, you can expect that the carrier will refund unavailable seats but will not follow bumping-denied boarding policies. Compensation for "split seating" fiascoes will probably be a test of your personal management style.
.
Gopi Maliwal in Hong Kong aptly asks, "How many frequent-flier miles do I get if I buy two or four economy seats instead of one expensive business-class seat? Twice or four times the miles, or just for one ticket?" Logically, you should earn miles for every seat that you pay for and use. But we do not live by logic alone! Faced with a subversive threat to yield management, airlines may argue that miles can only be allocated for one seat as only one person was actually traveling.
.
KLM specifically allows its Flying Dutchman members to claim miles for every seat they purchase on a flight under the multi-seat strategy. Would other carriers care to comment?