  Consider a randomly oriented graph $G=(V,E)$ and let $a$, $s$ and $b$ be
three distinct vertices in $V$. We study the correlation between the events
$\{a\to s\}$ and $\{s\to b\}$. We show that, when $G$ is the complete graph
$K_n$, the correlation is negative for $n=3$, zero for $n=4$, and that,
counter-intuitively, it is positive for $n\ge 5$. We also show that the
correlation is always negative when $G$ is a cycle, $C_n$, and negative or zero
when $G$ is a tree (or a forest).
