Quite a few people have complained they can’t easily find the share button on Google+. Here’s the UI:
The problem is that the Share button is below that Friends button. Friends isn’t really a button, more like a tag, but it looks like a button, and that’s what matters. Your eye is in the textbox (you’re typing), and the friends/more people crap stops your eye from looking below that for a Share button.
Easy enough to fix though.
Make the Share button more prominent (visually) than the friends button. And move it to a central place right underneath the text box. Oh, and don’t grey it out.
Something like this:
Fixed!
Peter Van Dijck 
Actually, it extends far beyond the Friends field.
Any “extra content” (photo / video / links … add a layer that disconnects the Share button and the textfield.
Probably a subtle “grouping” treatment forming a bloc of all those contents wld solve the issue.
In any case, it’s only a beta. We shld expect such glitches.
They put it below that friends button so you have to choose a circle to share it to. it forces the user to think about what circles to share it with.
Good observation, Peter. I briefly had a delay fInding the share button as well- for the exact reason you pointed out. For me, though, the expectation is the button to be on the right-hand side.