This Sunday's New York Times (registration required) travel section features a good analysis of international airfare passes that ambitious travelers may find useful. We at SmarterTravel have covered these offers individually in the past and the Times' Susan Stellin effectively points out who may benefit most from them.
Deals such as Cathay Pacific's All Asia Pass and Qantas' Aussie Air Pass are a good bet for travelers who want to visit multiple destinations in a region, and don't mind spending a good amount of time on planes or in airports.
Stellin notes, and I agree, that deals such as the All Asia, which allows for 21 days of travel to any of 18 Asian destinations for as little as $1,299, can save a lot of money for travelers who would otherwise book single trips to each destination. She also warns against some of the restrictions (fees for travel on peak days and during the high season, for example) that will add to the price.
Essentially, the most important thing to remember about airfare passes is summed up by a travel agent quoted in the article: "the more places you visit, the better the deal it is."