My understanding (please correct if I'm wrong) is that Sparks is about consuming content, and using signals (especially social signals) to better target that content to individual tastes over time.

A group is a social group, where all agree to be members. Let's say you have a set of 8 friends who love baseball and you all love to chat about everything baseball. In real life you get together frequently to watch baseball on TV, go to ball games, etc. and primarily discuss baseball. That can be done on Facebook, but not yet on Google+. You want "shared circles" where the name of the circle is the same for all 8 baseball friends and their chit chat about baseball only stays within the group.

People naturally group around interests like this. And online, it is a great way to filter noise and get relevant information.

I have a number of online acquaintances around my interest in passwords. At the moment, email is the most useful way to exchange targeted password information with them. One of us just started a password reddit - but that's kind of public and subject to the usual reddit nonsense. I follow 2 of them on Twitter but find most of the information not relevant to me because they have many interests besides just passwords.

In a private group setting, things could get more in depth, and stay focused on the subject in which we all have an interest.

Sparks isn't like shared circles as I understand. They just bring up articles on selected topics to be used as conversation starters. I like the idea but I think the implementation of sparks is a bit rubbish. I think Twitter does a better job in this space actually.

I was thinking the same thing. It's not clear to me though how the search results / feed in sparks is sourced. I assume it's a merging of +1 and shares with some sort of keyword matching, but it seems to show articles in random order and I haven't really figured out what makes it better than a google or twitter search. It seems like they are trying to make it better than a static group because it will include content from any user related to a topic, but it doesn't let me find other people who share my interests to add to my circles and it doesn't show me why something appears in the Spark feed.

The article was advocating for something more back and forth, like a chatroom or forum, rather than a newsfeed.

With Google+ just starting out (even at 10m users), there's already a feeling of exclusivity and community. Groups would definitely help keep that feeling going as Google+ goes public, though, as long as it's implemented right. With public circles, groups, tags, etc being advocated, I hope the simplicity of Google+ isn't lost.

people want subreddits.