Infant Google+ has a pretty privacy flaw already.
As the FT's Tim Bradshaw pointed out, despite the fact that you have private "Circles" like family and friends who only can see your content, anyone can "reshare" that content with their own "circles." That content can potentially then be reshared with anyone. Sort of like retweets on Twitter, content originally meant for private consumption could end up going viral.
Since the FT pointed out, Google implemented an interesting fix. Here's what we saw when we tried to reshare this image
