The Popular Post and Popular Question badges require 1000 different people to view the Post or Question. A number of Posts and Questions show that they have over 1000 views, but their creators haven't received the badge. This is because the count currently displayed includes all views of the page, including repeats from the same Member or IP address.
I just published an update that now allows you to hover over the view counter and have the number of unique viewers appear in a tooltip. This should be useful for people curious to see how close they are to earning those two badges.
Software Developer, Maplesoft