In the Stack Exchange Data Explorer, the Ask Ubuntu logo is shown as:
This is the image being displayed: https://cdn.sstatic.net/Sites/askubuntu/img/logo.png
when indeed it should have the "speech-bubble" portion visible. Looking at the image carefully shows that it should (if I am correct) be transparent around the white speech bubble, which isn't visible at all. Some users, as seen in comments below, believe that the icons from the site list should be used, which I agree with.
I wasn't sure whether this belongs here because it is about the design of the Data Explorer, or on Ask Ubuntu Meta because of the logo design, so feel free to migrate if it is in the wrong place.