Recently Updated List has users that aren't in current group

When a user updates info, this shows up in EVERY user's Recently Updated list; we want to use Confluence as a customer information portal. If this is the case, Customer1 will have users that can see updates for Customer2 users. This seriously impedes our ability to use this product.

If User1 is in the group Customer1, and User2 is in the group Customer2, and they're not in any shared groups, why can they see each other in Recently Updated or in the People Directory? Some ability to control this would greatly increase the utility of this implementation.

Thanks!