After last week's performance and quality update to Hangouts, Google has rolled out yet another big change to the video call service. As of this week, a Google account or sign in is no longer required to talk with others, or for them to talk with you.
Google says it wants "simple, easy access to meetings" and so they're breaking down the barriers. Now all that's required is clicking an invitation link, and you're in.
Of course, if you want to set restrictions on who can join, that's definitely an option, as is muting and kicking people.
The change should be in effect now if not later this week.