  In this paper we investigate the quantity of diagonal quartic surfaces $a_0
X_0^4 + a_1 X_1^4 + a_2 X_2^4 +a_3 X_3^4 = 0$ which have a Brauer-Manin
obstruction to the Hasse principle. We are able to find an asymptotic formula
for the quantity of such surfaces ordered by height. The proof uses a
generalization of a method of Heath-Brown on sums over linked variables. We
also show that there exists no uniform formula for a generic generator in this
family.
