Why does my foursquare point total keep changing?

For users accustomed to the old foursquare leaderboard (I’m told there are some people who actually paid attention to it), the most confusing part of the new leaderboard is that it no longer resets at midnight each Monday. Point totals are now calculated over the previous seven days — down to the second.

That rolling seven day period can make it seem like your points are disappearing. In reality, they’re just falling out of that window.

Under the new system, your points — and those of your friends — can change on a minute-by-minute basis. The change makes the leaderboards more dynamic and fun. It’s now impossible for someone to get an insurmountable lead on Monday morning and dominate the rest of the week without checking in on a regular basis.

PS. Given all the possible combinations of points, what are the odds that three people would be tied on my leaderboard with the same high point total?