top active users

So we were having a discussion today in the office about how to determine a list of the top active users on the site and came to the conclusion that it would be a good feature to have within the activity module. We also discussed what qualifies a user as a top active user. Logically you'd think that the person with the most activity on the site would be the top user, however there could foreseeably be some customization needs in this area, such as weighting different actions to be worth more in acquiring 'top user' status, and maybe wanting to promote users based upon said status/es. This is something that is handled by such modules as User Points and userpoints_role (http://drupal.org/project/userpoints_contrib). So maybe after finding a way to handle 'top users' we can look at making sure there are integration points for userpoints.

Votingapi has a cache table for keeping track of the amount of votes for a particular node and as this feature could potentially become expensive by just querying the activity table, we'd probably want to handle this in a similar fashion.

Thought?