Earlier quoted context omitted.
So, are you okay with the idea of the entire world seeing all your emails, or don't you use email?
I wouldn't say I'm "okay" with the idea of the entire world seeing all of my emails, but I accept that it is a very real possibility given the extremely insecure nature of SMTP and the other protocols involved in email handling, so I don't send (or request) anything via email that is very private.
Not to mention that the transport mechanism for pictures on G+ is much safer than email, since it only goes through one server (unlike email, where there's usually at least two MTAs), and all transmission is done through HTTPS.