Anyone can do it.
The themes or purposes are unlimited.
A group can be private or public. It can be established as open to anyone who wishes to join, or "By invitation only"
Examples of Private Groups: A consortium of artist members may wish to have their own virtual meeting and communication center. Formally established associations such as regional guilds can create their own private groups, as can gallery groups. The Gallery Groups can use their virtual meeting place to link to their web sites, and launch event announcements to the entire network community. A Regional Guild, for example, can put a Calender of Events, or a an Update Member Info space and link to Paypal collect annual dues. Since anyone can request an invitation to join, artists seeking membership can be sent a provisional "Sign-up" Information email with a link to Paypal for payment of membership fee.