My office is downtown, so invariably there the usual assortment of urban campers (homeless) people running around scavenging cans, bottles, and cardboard. They also set up camp in any semi-secluded spot they can.
One of the major problems is that there is a lack of public restrooms in the area. This leads to the bums dropping trou and relieving themselves wherever they can. Most of the time this is in an alcoveoff the alley that contains the back door to one of the businesses. This leads to the "bumstripe" of runny s**t where they have balanced their ass against the wall and let fly. Needless to say, this is rather disgusting, and rarely gets cleaned up, leaving a fly attractant and general disgusting smell. It's bad enough that there's the stench of rotting food coming from the dumpsters, but the added aroma of feces and urine jus makes it that much worse.