I am sure you've heard the news, if not, you will soon that Gmail is letting those with Gmail and Google+ email anyone with Gmail and Google+, without knowing their email address.
In short, Google is rolling out a feature within Gmail and Google+ to allow anyone to email anyone, assuming certain settings are on. Danny Sullivan sums it up saying "Spam city! Potentially, but Google has some safeguards built in that it hopes will keep this as a useful feature rather than a nightmare." You can read his post on how to "safeguard" your account from the unwanted spam.
What is funny is that Google's Andy Bohm, a privacy advocate for Google, said on Google+, that you need to learn how to "stop worrying and love the GMail."
He then explains step by step the concerns and why Gmail still works for you and people concerned with privacy.
So if you are concerned, go learn why you MUST stop worrying and love "The Gmail" at his Google+.
Forum discussion at Google+.