Free dating and social networking sites
In the context of the internet, this is what social networking is, except online.
Over time, the main/home page of the social networking site can easily gather hundreds or thousands of threads.
This is especially helpful considering some social networks don't show you who has seen what you posted.
A primary focus of groups is to create interaction between users in the form of comments or discussions, which is why most social networks support commenting on nearly every type of post.
Some social networks use groups to help you find people with similar interests or engage in discussions on certain topics.
A group can be anything from "Johnson High Class of '98" or "People Who Like Books" to "Doors Fans".