From CS 294-10 Visualization Sp10
Example of a good visualization is this combined visual of a carbon bath tub. This visual displays a lot of information such as sources of CO2, their relative percentages, how much they add each year, in total and how this CO2 is dissipated, what are the relative speeds and sizes of the outlets and how they are way less that the CO2 sources causing the bath tub to fill up as we go.
Example of bad visualization is this Stauer watch. Watch just has 3 numbers (H,M,S) to show (effectively) and there is a convention of CLOCKWISE/CounterCLOCKWISE directions which is followed everywhere. In this watch, the way to read this watch makes it contrary to natural way of reading a watch. Generally one reads a watch as, if the hour hand is just past 5 and the minute hand is just past 20min mark, then the time is something like 5:23. But here, since the digits are marked in reverse order, just "past" 20 min mark is actually 17 and NOT 23. Similarly for hour hand. I find this slightly odd and given the fact that clock is viewed for a fraction of second, I think there are high chances that correct time is never deciphered.
(Sources: Carbon bath tub is from December issue of National Geographic and Stauer watch is from their website as well as from Delta airlines SKY magazine.)