I don't lock my bags but rather just make it hard for someone to reach in easily. A piece of wire wrapped around a couple times prevents the quick grab but still allows the TSA to look inside when they see the huge amount of metal. I get an inspection notice when I move my climbing gear almost everytime (especially with ice tools).
I have had no problems with rope, harness, and biners on the plane. I have been stopped pre-9/11 with my trad rack, so I can only imagine that this might be a problem now. I have been putting my rack in my check bag wrapped in my sleeping bag.