Ran afoul of the law.
Even on the beach, you might occasionally run afoul of authorities or parents who would rather their children not see a virtually naked woman in the water.
Second, if a MySpace friendship turns into something more, don't run afoul of any workplace regulations concerning dating.
Most seem to be living fairly normal lives, some have managed to eke out a few more moments in the celebrity spotlight and a few have run afoul of the law.
In the pilot episode, they run afoul of the Kazon, a race of bad-hair warrior types who steal technology and set their sights on owning Voyager.
The dwarves run afoul of goblins, are captured by elves, meet a shapeshifter in the wild woods, and in general have a lively time in their attempts to reach the mountains of their ancestors.