I've had lots of bikes like that that I never lock (theft isn't too bad where I live). That's WHY I have bikes like that so I don't have to lock them. The bikes cost less than a good lock, and the convenience of leaving them unlocked outweighs the risk of losing them. On the other hand I've got a friend who got his bike stolen from work, and replaced it with a Schwinn Collegiate which he bought for $60. He always locks it now, and he's right to do so. If you care if it gets stolen, put a lock on it.