You can share with them by making your post "Public". Conversely, there's a wild-west "Incoming" section you can browse which contains posts by everyone that ha

You can share with them by making your post "Public". Conversely, there's a wild-west "Incoming" section you can browse which contains posts by everyone that has put you in a circle (whether you put them in a circle or not). To be clear: it's asymmetric so you don't have to "approve" followers or not. Feel free to put anyone in your circles, and you'll see their posts if they make them public, or if they post them to a circle they've put you in previously. You get notifications when people add you to a circle, so you have the opportunity to add them to a circle if you want, but it's not required. Whether it's socially expected (as it seems it used to be on Twitter), is something of a debate among G+ users currently.