The Death and Life of Great American Cities, by Jane Jacobs

There must be eyes on the
street, meaning that inhabitants
and owners get involved what
is happing on the street. People
who notice what goes on in
the streets and which can take
action if necessary.
It is important that the eyes
which watch a street can generate
a feeling of trust to the
people on the streets, in order
for the community surveillance
to work, to know if that guy is
just hanging around or if he
seems to have bad intentions.
This trust gets built up by many
small social activities which
happen in a community, which
build a community identity.
This is something that can not
be provided by an institution,
these contacts have to come
from the people.