Looking at some of the protests, I just see it as a final effort to embarrass Reddit. I think they have collectively decided that the only way to inflict actual, financial harm on Reddit is through the IPO or the advertisers.
thus you have some subs surfacing porn to piss off the advertisers, and some subs going private until reddit deciding to break up the mod teams against community consensus potentially damages trust in the website generally to hurt the IPO
I think it will probably have some effectiveness in the medium term, but I also think it could have been more effective if all the protesting subs called reddit's bluff and refused to reopen. The more drastic the action on reddit's part, the more drastic the media attention, IMO.