My Twitter account is locked. I may be paranoid, but I prefer to have some degree of control as to who sees the ruthless truth that I tweet. From time to time I'll get a follow request from someone who is following 16,000+ people and is followed by a similar mob. Excuse me, potential follower, are you sure you're even remotely interested in anything I have to say? I think not, and I have no desire to be a bump for your statistics. BLOCK.
My philosophy of Facebook connections is even more restrictive. The only people I connect with on Facebook are a) people I know and b) proven MST3K fans. Other people are free to rifle through the White Pages to look for "friends".
I'm still working on my Google+ philosophy. Rest assured that it will not be "open to the world". I only post to people in my Circles. Sometimes I only post to "close friends". If there is any personal revelation in my post, I disable re-sharing.
The uncomfortable side of Google+ is when an innocent, unknown person adds me to their Circles. I refuse to blindly add to my Circles anyone who adds me to their Circles. Just because someone is nice enough to add me to their Circles doesn't mean that I will now consent to sharing my personal life with them. It's rather tame in these early days, but once the Marketers suss out the cracks, we G+ folk are going to be bombarded with spam. I trust that Google will find a solution to this future problem. For now, on Google+, I add no one to my Circles unless I truly know them. So, apologies to all you nice folks that I don't know at present and who decide to add me to your Circles on G+. Once Google+ is a more mature product, there may be a way for me to acknowledge your graciousness.