My users were complaining they couldn't see some avatars on my forum. I realized it's because I generate a UUID for each upload and bucket the files into folders such that a hex ID of "ad73a7a8b9" has the URL of "/ad/ad73a7a8b9".

I realized the blunt force approach of various adblockers will block anything on "/ad/...". Some would even block "/ad...". I found that a bit annoying.