I asked about this on Community Building SE a while ago and got good answers. <a href="http:&#x2F;&#x2F;communitybuilding.stackexchange.com&#x2F;q&#x2F;711&#x2F;530" rel="nofollow">http:&#x2F;&#x2F;communitybuilding.stackexchange.com&#x2F;q&#x2F;711&#x2F;530</a>