One thing I recall from William Whyte's fantastic The Social Life of Small Urban Spaces is one idea about people: people like other people (so we like people watching), but some people (typically who own, maintain, or work next to a small urban space) don't want "undesirables" in that space while "undesirables" don't want other people around and so you want things like benches.
Here in NYC, we have some recent citywide benches. People can sit, relax for a moment, and watch other people. Passersby might feel a little better with some other people sitting there. But, what's interesting about these benches is the little raised seat dividers -- people can't sleep on these benches, probably addressing the "undesirables" issue that Whyte wrote about, while the rest of the bench lets people sit there, as we like to do.
