This blog entry is part of a series of reflections on the multi-site model of church. After the whole series has been posted, you can do a search for multi-site within the blog to pull up the whole series.
I know some multi-site churches may handle this differently, but here’s my unvarnished opinion: localize the small group ministry. If the people who are in a small group together attend different sites, you are forfeiting the benefits of multi-site (increased community, ownership, and small church feel), and only incurring its higher-maintenance costs.
Localizing the small groups also allows for better support and coaching of the leaders, and provides allows the groups to serve together in the Sunday services (greeter team once a month, etc.). If community is not localized at the site level, there is really no point in doing multi-site– megachurch is much easier and more cost-effective.