Tried to run postgres -D /usr/local/var/postgres
and got this:
FATAL: could not open directory "pg_tblspc": No such file or directory
An easy fix. The Yosemite install blows away some empty directories that PostgreSQL expects.
mkdir /usr/local/var/postgres/pg_tblspc
mkdir /usr/local/var/postgres/pg_twophase
mkdir /usr/local/var/postgres/pg_stat_tmp