Yes, that's true. I suppose you could always just move them to a circle that you never share with. But I agree that, if this is really a problem, it's best not to have a Google+ account at all. (You've got to admit, though, this is a pretty contrived scenario. Someone that runs their own web server can also tell that you've never visited their site, for example.)
You can hide whether the list of people who you are following shows up on your profile. You can't, AFAIK, hide the fact that you are following someone from the person themselves.
In other words, if you have person B in your circles, you can hide whether person C (or the general public) can find out that person B is in your circles. You can't prevent person B from knowing that they are in your circles (thought they won't know which circles they are in).
I'm pretty sure this is the model. I can confirm it if you'd like.
I'm not sure. I enabled G+ to manage our business page, which made my account visible. The couple of people who found it added my personal account from knowing my email. I circled them mistakenly (a slip of the mouse is all that's needed) and then uncircled them. They get a notification that I am, indeed, on G+ and am now ignoring them.
Knowing this beforehand I would have made a new email address to manage the account, and could freely allow circling. I guess I'll go find out now if I can change the owner of the page.
