User blog comment:V3hemenc3/Runic Bulwark and who on your team should build it/@comment-4124337-20130201173306/@comment-4434162-20130202075707

the item actually does stack, however it doesn't stack the whole way, just for the wielder.

for example, when a jungler has a bulwark, and the support has another, the jungler gets the stats from his own bulwark and the aura stats from the support's bulwark.

at least, that was the way on S2 Aegis, might have to check it here.