"First, when you have a post that is defined as Limited (anything that you haven’t shared publicly) other people will no longer be able to share that content. Previously, once you shared it, others could link to it and that created a privacy problem that Google wanted to fix in the post-Buzz world."
The original title worked just as well.
While we don't normally think of it as odd (probably because it happens on Facebook and other social networking sites all the time) Google+ was meant to protect privacy better than this, so it's a valid concern. And they're addressing it, as you noted.
I think you should be able to share links again, without giving access to all the comments and such. Pics and text should not be sharable... Without permission. I can imagine having things that I don't want to post 'public' but that I wouldn't mind friends sharing with friends I don't know.
The only solution against it, which I'm able to come up with quickly, is Google Plus adding subtle watermarks identifying uniquely each recipient.
I'm a little more concerned with the fact that you can see who a limited post was shared with by clicking on the limited link next to posts. It should be pretty simple to figure out who your friends have placed in their circles by looking at who their limited posts were shared with.
The UI fluff will never change that.
