The vBulletin software did not have an option to automatically "subscribe" (a notification when new discussions are started) a person joining a group when a person joined a group (the person had to manually "subscribe" to the group using the "Group Tools" drop down menu which is on group pages. As of 2011-06-26 anyone who joins a social group here will automatically be "subscribed" to the group. You will receive a daily notification by email when one or more people start a new discussion. If no new discussion is started you will not get an email. You can turn off daily notifications, or opt for a weekly notification instead of a daily notification, by using the "Group Tools" drop down menu which is on group pages.

If you are currently a member of a social group, unless you knew of the "subscribe" option and "subscribed" at some point you will not know when someone starts a new discussion unless you visit the group. If you are a current member in a social group and are interested in keeping up with what is going on in the group (or groups) you have joined without having to specifically visit the group every day (or however often), please use the "Group Tools" drop down menu to "subscribe" to the group.

I am "subscribed" to the group in the picture so the below shows an option to "unsubscribe". If you are not already "subscribed" the option will be there for you to "subscribe" instead of "unsubscribe".