My wife and I love bike touring but flying with our bikes as non-standard luggage had become prohibitively expensive, as much as $250 one way for one bike. We did a tour along the Danube on rented bikes and they were horrible. We rented bikes twice in Alaska. One set was junkers. The other was okay, but obviously not personally fitted, so not quite comfortable for long days in the saddle. I knew about folders, but thought they were intended only for commuting and would be unable to meet the demands of multi-day touring.
Then an acquaintance who also tours told me about Bike Friday. Fridays are personally fitted and built to each buyer's specs. They are tough. People have ridden them around the world and even raced them in European Classics just to show what the bike is capable of. Fridays are also expensive, so I did a lot of research, comparing them to other brands. Ultimately, I decided to spend the extra money because we would have exactly the touring bikes we wanted; no compromises necessary. For example, we bought ours with 27 gear combinations ranging from 18 to 106 gear inches and a frame that will handle tires as wide as 42mm and still accept fenders - well suited for loaded touring, even on unpaved roads. (Not European Classics. though)
Bike Friday starts by cutting tubes to accommodate rider measurements and preferences, then building the bike with exactly the parts one wants. (stems, gearing, seats, cranks set, brakes, pedals, tires etc.) Except for the folding frames, all parts are industry standard. If you need repairs while on tour, a local LBS can work on them and get replacement parts from the shelf or the nearest supplier. In the unlikely event of frame damage, the frame is high quality steel, the easiest material to get repaired anywhere in the world. The best part is not that these bikes fold, though that occasionally comes in handy, but that they quickly disassemble into ordinary Samsonite cases meeting airline size and weight requirements. They fly as standard luggage. We've used them all over this country and in Europe. In January we will take them to Viet Nam. I have four other bikes (good ones), but the folder is my favorite ride, even at home. It is durable, dependable, quick and comfortable. A hand built Friday IS pretty expensive. For commuters, I think some other folders are better (e.g Moulton, Bromptom) and most are more economical. But for touring, a Friday is worth every penny if you can afford one.
Should folders get more attention for every-day use? Probably yes - they can certainly make commuting easier. But the trend seems to be toward bike-share programs, which have the advantage of taking up zero space on trains or buses and taking zero time to carry on and off.