This would be so much more useful if it were based more heavily on comments. Right now, it's just "people who made a popular top-level post in the last month", which is information you can easily find by just scanning the front page.
Even though I'm the one who originally suggested weighting top-post karma more than comment karma, I've felt that 10 karma per vote for a top-level is a bit too much. Five karma would seem more appropriate, weighting top-level posts more but also giving a more realistic option to climb in ratings via comment karma alone.
I wonder if a "top 100 contributors" page, with both all-time and 30 day options, would be a good or bad idea. It might more effectively encourage participation, but also make people more addicted and possibly cause undesirable status dynamics.
Is the karma shown that accumulated from posts and comments that were made within the past 30 days, or from all votes on all posts within the past 30 days, regardless of the age of the post or comment?