One isn't necessarily the loneliest number. The travel industry is finally realizing that the days of Noah's Ark — when travelers vacationed exclusively in pairs — are long over. Norwegian Cruise Line made a splash when it announced that the Norwegian Epic, a cruise ship debuting in summer 2010, would have 128 cabins designed for solo travelers. (Traditionally, anyone who wanted to cruise alone would have had to stay in a double cabin and pay a "single supplement" to make up for the lost revenue.) The studios are only 100 sq. ft. (about 9 sq m), but there's a communal living room where solo travelers can hang out. The bigger drawback is that the cabins are all on the inside of the ship; their windows all face the corridor. Still, if there's enough interest, more cruise lines are likely to follow in NCL's wake.
Likewise, hotels like New York City's Jane are introducing rooms for singles — they're tiny (50 sq. ft.!), but the idea is that solo travelers are unlikely to spend time lolling around inside.