Being seen on the road is important. Cars weigh more than cyclists and it is likely not to end well for the cyclist if there is a collision. As I wrote in my 7 Non-Bike Products Essential for Bike Commuting post, it takes 16 batteries to power all of the lights I use on a night commute.
While in Washington D.C. recently I stumbled upon a bike that definitely caught my eye -
It took me a minute to figure out what I think is going on with this. The sunglasses in question have lights at the end of the temple pieces. I think they are probably meant more for runners to use at night, but this hacker seems to have tied the glasses to the back to serve the purpose of a rear light.
This is an interesting interpretation of "I wear my sunglasses at night."