In the instance involving the inflatable brick, personally I don't think it's an effective piece because it's execution is, if I understand its methodology correctly, dangerous. Protest art should be just that: art that gives visible resistance to a topic or issue. This does not entail anyone or anything being harmed in the transmission of this message or mantra. Putting people in danger will have the opposite effect than what the artists would have wanted; the public would condemn them and their cause for resorting to such dangerous tactics.
The feminist art featured in the second article to me is fairly effective at communicating the frustration with men in the past and in current times. I do think that the magazine cover piece was especially clever, using a story about women trapped in DC museum basements to symbolize the hidden art by women, and society's validation of male artists more than female artists.