…you might want to consider the risk factors.
When you enable members to create groups on your community you’re essentially renting them your brand name (and a small portion of the audience) to pursue their own goals.
A few things to consider:
1) Which members will you allow to create groups? Can anyone do it or only a select few who have demonstrated the ability to manage a group (hint, choose the latter)?
2) Do you have a training program for members to create groups?
3) What happens if group leaders don’t crack down on minor abuse?
4) What happens if group leaders don’t crack down on serious issue?
5) Will you allow multiple groups on the same topic or only one group per topic?
6) What happens if a group leader becomes inactive (who can replace her and what does this process look like?)
7) What happens if a group leader is active but the group isn’t? What level of activity does a group need to continue as a group?
8) How will you remove groups which don’t take off without upsetting group leaders or members (and what will you do with the content in that group?)
9) Who gets to name the group? What are the restrictions on group names?
10) What happens if groups are local and want to meet in person? What is your legal liability for what happens? To what extent can you support groups?
11) What happens if group leaders get together to demand changes you are unable or unwilling to make?
When groups work well, everyone wins. When it doesn’t, you can upset your best members, building hundreds of ghost-villages, and see your brand name tarnished.