My company uses PowerShell to manage the members of thousands of groups. There are SQL statements and other "rules" that govern who should be a member of a given group. This solution does not really lend itself to creating groups and then nesting the groups within larger groups... it just adds users to groups.
These security groups are rarely used for securing resources... when we do, we tend to create a group to manage the ACL, then drop the mail-enabled group into the ACL group.
My question is: Is there a threshold number of users where I should really be thinking of nesting groups rather than adding people directly? We have < 3000 people in the entire company.