NEW YORK — Google just announced a big change that, as far as I can tell, no one was asking for except perhaps the people who run Google+, its failed Facebook clone.

Starting this week, the feature will let anyone with a Google+ account send emails to Gmail users, and vice versa, unless the recipient has opted out. Here’s how a Google product manager explains it:

Have you ever started typing an email to someone only to realize halfway through the draft that you haven’t actually exchanged email addresses? If you are nodding your head ‘yes’ and already have a Google+ profile, then you’re in luck, because now it’s easier for people using Gmail and Google+ to connect over email. As an extension of some earlier improvements that keep Gmail contacts automatically up to date using Google+, Gmail will suggest your Google+ connections as recipients when you are composing a new email.

That sounds potentially useful if you’re the sender – and rather invasive if you’re the recipient. Google does let you opt out, and every Gmail user will get an email from the company notifying them and pointing them to the privacy settings when the feature goes live.

But a Google spokesperson confirmed to me that the default setting will be “anyone on Google+,” so you’ll have to change it if you don’t want strangers cluttering your inbox. Some critics have quite understandably objected to Google’s making this an “opt-out” rather than “opt-in” feature.

Google is careful to note that people who send you messages in this way don’t actually see your email address. In some ways that seems like splitting hairs – who needs your email address when they can send you emails without it?

But there is a difference, in that strangers can only email you once using the Google+ feature. If you don’t reply or add them to your circles, they won’t be able to keep spamming you. Additionally, when someone who’s not in your Google+ circles uses the service to email you, it will go to your “Social” tab in Gmail rather than your “Primary” tab, provided you have tabs enabled. That’s yet another reason to go ahead and enable them if you haven’t already.

On balance, it sounds like this service had the potential to be convenient without being invasive – if Google had made it “opt-in” instead of “opt-out.” As it is, my guess is that it’s likely to annoy and confuse a lot of Gmail users who barely even know what Google+ is and won’t understand exactly what it is that Google’s asking them. A Google spokesperson acknowledged that there’s something to be said for “opt-in” policies from a privacy standpoint, but told me that Google felt it was better on balance to make it “opt-out” so that people could first see what it is they’re opting out of.