To measure success for Facebook Groups, I would consider a number of metrics. First, I would look at the number of active groups and the number of members in those groups. This would give us an idea of how many people are using the platform and engaging with others on the site. Secondly, I would consider engagement metrics, such as the number of posts, comments, and likes within each group. This would give us a sense of how active and engaged the community is and whether they are finding value in the site. Thirdly, I would consider retention metrics, such as how frequently users return to the site and how long they stay on the site each time they visit. This would give us an idea of whether users are finding the site valuable over time and whether they are likely to continue using it in the future. Finally, I would consider revenue metrics, such as the number of ads served and the revenue generated from those ads. This would give us an idea of whether the site is monetizing effectively and whether it is a sustainable business model. Overall, success for Facebook Groups would be measured by a combination of these metrics, with a focus on engagement and retention as the key drivers of long-term success.