I noticed a little yellow box pointing to this when I signed in this morning.
Previously, I recall a way to allow chat for certain circles, but I guess the privacy concern of revealing your email address to people in that circle when you hadn't necessarily enabled that for the circle was an issue. They are back to the old Gmail style of inviting people to chat, however it looks to me that people in circles I previously enabled for chat are now grandfathered in. I don't have a problem with this, as I'm not that protective of my email address, but I also only have one person that fits this critera. Anyone else seeing this?