We show lower bounds of $\Omega(\sqrt{n})$ and $\Omega(n^{1/4})$ on the
randomized and quantum communication complexity, respectively, of all
$n$-variable read-once Boolean formulas. Our results complement the recent
lower bound of $\Omega(n/8^d)$ by Leonardos and Saks and
$\Omega(n/2^{\Omega(d\log d)})$ by Jayram, Kopparty and Raghavendra for
randomized communication complexity of read-once Boolean formulas with depth
$d$. We obtain our result by "embedding" either the Disjointness problem or its
complement in any given read-once Boolean formula.