For about a year (2008/2009), I took a picture with my phone of the ashtray at work where I smoked. What I found interesting is that I never saw anyone smoking, drinking, or eating at this ashtray. The ashtray was on the roof of the building I worked in. Apart from the times I smoked with a coworker, I rarely saw anyone up at the ashtray doing much of anything. And yet, the activity is clear. Empty bottles. Paper cups. Discarded Ramen containers. Cigarette butts. Other junk.