Death by ten thousand paper cuts.
So your website is becoming popular. That is really great but have you checked your utilization logs lately? Scott Hanselman noticed that his favicon.ico was taking up a 27 Gigs of bandwidth a month! That was about 11% of his total bandwidth usage.
What is the FavIcon? It is the little icon in your address bar. It is normally an image that is 32x32 or 16x16 pixels in dimension. Not that big right? That image was 70k for Scott and after a few tweaks, he lowered it to 4k. After he did some math, that reduced his bandwidth to just about 2 Gigs.