I carry a U-Lock on tour, and always carry my money, passport, and other valuables with me. I usually secure my bike to something seriously immobile when I leave it... but context is everything. While on a tour in Switzerland a few years ago, my bike needed a small repair. I arrived in a town, found a bike shop, but it was closed for lunch. Outside the store, there was a display of a dozen or more VERY expensive racing and mountain bicycles... all unlocked! Needless to say, I did not bother locking up in that town!