I hear the LJ folks are paying attention to this.
The uproar is not about being able to x-post your LJ posts, it's about others being able to share their comments to your LOCKED posts on FB/Twitter, thus perhaps giving things away about your identity or post.
I know I would not appreciate that!
I think my friends are sensible enough not to want to do such a thing and I certainly have no plans to. :)
If LJ wants to add a cool feature, why don't they appear in the "Share" options all over the 'net nowadays and make it really easy to share links with our friends?