We made a slight change in the way popularity is being calculated, as part of a bigger change to that system that is coming soon. Now, a person's popularity is penalized for inactivity -- so people who joined the site 6 months ago and never came back (but happen to be SUPER HOT) will not dominate the popularity charts.
If you are reading this, this change means there is a good chance that your popularity just went up a few points.