Say you get a badge that requires you to get 10 votes. You get the badge but then someone down votes you so you no longer have the 10 votes.
Does the badge get pulled?
Say you get a badge that requires you to get 10 votes. You get the badge but then someone down votes you so you no longer have the 10 votes.
Does the badge get pulled?
There are 2 kinds of badges--general badges, and tag badges.
General badges are the kind most frequently discussed. Each one is awarded based on a separate condition. All their names are capitalized and most are a little bit silly.
General badges are never automatically revoked. General badges do not express that their holders continue to meet the requirements to have received them, only that they met those requirements at one time.
For example, if you earn a Good Answer badge, that means one of your answers had a score of 25 (that is, 25 upvotes, plus one upvote for every downvote). If your post has a score of 25 and then gets downvoted (or unupvoted), you don't lose your Good Answer badge.
However, a general badge may be manually revoked if you got it by "henious cheating." I believe such removal requires the involvement of a Stack Exchange employee. An example of a badge earned "heniously" is if you get your Good Answer badge by creating 25 additional accounts and use each one to upvote your post. In contrast, if you get your Critic badge by downvoting something but then removing the downvote, that is not "henious."
Tag badges reflect your number and distribution of upvotes in a tag in real time, and are automatically revoked when your score drops too low (and are re-awarded later if the necessary score is again met).
For example, I currently hold the sudo badge. If my total score in that tag dropped below 100, or if it remained at or above 100 but my number of upvoted posts dropped below 20 (as could happen if posts were deleted or if votes were changed), then I would automatically lose the badge.
My understanding is that community wiki posts do not contribute to tag badges (though they do contribute to most general badges). So previously non-CW posts becoming community wiki can also cause tag badges to be lost.