Leaderboard should have a weekly or monthly ranking as well
The current leaderboard shows your total score for all time. To promote people continuing to practice, there should also be a weekly or monthly leaderboard. That way, even if you started later than your friends, you can still compete with them to have the best weekly score, and people with high scores will have an incentive to keep coming back.
As an example of a similar system, Stackoverflow displays the weekly leaderboard as the default, which gives new users who have had a good week the chance to show up along side the most dedicated long term users.
Is there a community leaderboard for everyone who uses duolingo, I would like this feature as I can compare how I am doing against other people as I have no friends. (people can opt out if they want but peoples scores should be opt in by default)
If you add friends on Duolingo, you will see a personal leaderboard, comparing your skill points ranking to theirs. But it's for all time, so a new user will start out way behind an experienced user, and if they keep using it approximately equally, will never catch up.