Theres a lot of other ways you could handle it. For example, Type Race could have goals based on the percentage of players who have logged in in the past x months and are on y team. It wouldn't be based on interactions per day or something. That example isn't perfect (some teams get stacked with players who go NUTS, and giving them a lower goal wouldn't be fair), but it's an example of how you can use site statistics other then just daily sitewide interactions.