It handicaps honest people.

Does it necessarily? I think it depends on the context and the environment. Sure, a senator isn't going to tell a reporter all of his signaling intentions, but we're in a rationalist environment, looking for the truth. People also appreciate honesty. One of my hidden agendas for this post was explicitly bringing out my previous hidden agendas, in order to promote them better. I don't know if it was the best strategy possible, but if somebody else had come up with the idea before I did, I think I'd respect them more for it, not less.