Posterous, the email based blogging tool, has quietly (or not so) built a very large user base. The tool’s popularity I believe is in large part due to how simple it makes it to engage in the act of blogging. Users post content by sending an email .

While it is indeed a simple tool some very well known bloggers such as Mashable editor Jennfier Van Grove and Edelman Digital’s Steve Rubel have moved to it as one of their primary sources for information streaming.

Actually, while many people swear by Posterous as an information posting platform I haven’t really seen it as particularly powerful tool for small business over any other platform such as WordPress.

This week, however, Posterous added a feature that I think may have some real utility for small businesses.

Posterous users can now create their own public or private groups and add users that can share, post, and submit various form of content. Again, using email only, group members don’t even need to have a Posterous account to add content. The two panel interface presents the information in a very accessible way.

Groups have been around for a long time from Yahoo and Google, but I think this platform is a much better tool for multi-party sharing around specific topics of content much like a forum with better structure, more types of content and let’s face it a higher coolness factor.

I can see:

• Business units in organizations using the tool to archive content
• Loosely formed networks sharing information as a group
• Small business teams creating and sharing information
• Customer groups creating what amounts to user generated sharing
• Organizations building community around shared ideas
• Non-profits building groups sharing around an event
• This might also be one of the best family sharing tools out there too

To  create a group all you need to do is send an email to new [email protected] and tell them the name of the group. You can then add a list of group member. Posterous will send your member an invite and create the URL for the group blog.

All groups are private by default, but I could certainly see public uses for the tool. Group owners have the ability to see permissions for members.