I just dropped some cash on a Yakima car rack and a bike carrier. The Sales person at my LBS said that it wasn't worth buying the locks because a theif would most likely steel the entire car rather than just the rack. Also, the bike carrier is very inconvient when it comes to taking it off, so I won't be taking it off everytime I'm done transporting the bike.
I would like some honest opinions/stories so I may make an educated decision on this purchase (locks aren't cheap!) before me rack walks away.