+1 on the "locks." A fairly light cable and small lock are all you need to deter opportunistic theft. And keep in mind that a u-lock doesn't come in that handy outside the urban setting.
I guess I'm the "dissenter" when it comes to locks as I bring the same locking system (U-Lock plus cable) that I do in the city. For one, it's in the same spot(s) it would be for around town riding. And because its always a part of the bike, I don't think about removing it. I realize that yeah it weighs more than a fairly light cable lock, but I'm more for peace of mind than weight reduction with this one item. It's also worth considering where exactly one is touring. Through rural areas I don't always lock my bike (or sometimes I just "hobble" it.) But my tours tend to incorporate some cities so I like that security. And it doesn't always have to be big cities, sometimes college towns are pretty notorious for bike theft (Eugene, OR for example.)