User blog comment:Emptylord/Season 3 - PBE Patch Notes/@comment-50.141.54.109-20121126224751/@comment-4909453-20121127013222

Regardless that the supports (excluding tanky supports) can still build Bulwark or just stop at Aegis is an option for them. The supports is try to last in the teamfight as long as possible providing whatever is essential during trades/harasses/teamfights. So for now, Aegis has been a favored item to be built, but this also depends by how much gold they end up with if they have the gold to finish aegis.