WordPress.org

The Acts as Group plugin provides a means for communication on multi-user blogs. You can create user groups for any purpose. It also allows you to communicate with other users through a Twitter-like interface on the WordPress Administration Panel.

Who should use the Acts as Group plugin?

Acts as Group is designed to help people who participate in multi-user blogging or group blogging. If you are seeking a simple way to communicate among members and don't want an overly complicated solution, Acts as Group is your best choice.

Is this a Twitter client? Does it require a Twitter account to use?

No. Acts as Group is not a Twitter client and you don't need a Twitter account to use it. Only a user account on the WordPress blog is needed.

Who can see the group messages?

Only group members can see the group messages. Its interface is closed so that your privacy is securely protected.

We use P2. Should we switch to Acts as Group?

You don't have to switch, but if you desire a more closed way of communication, Acts as Group would be a good option to try.

Does this support WordPress MU?

Yes, of course.