I'm the original poster, and thought I'd summarize what I've learned since I started talking to people about this subject. I've been getting lots of different responses to my posts/email, ranging from total dismissal of reviews/juried shows to total support of what they do. I guess my conclusion from what I've learned so far is that these places (for the most part) aren't making a buck off photographers, and that they couldn't do what they do if they didn't charge enough for it (I read for instance Laura Moya's detailed description of how critical mass works over at "a photo editor"). Moreover, if one were actually to try and get meetings w all the people who see one's work in these venues, one would probably end up paying quite a bit more, if it were even possible.
On the other hand, there are certainly many photographers (some of whom wrote to tell me)who have either severely curtailed their participation in such events, or ended it completely primarily for financial reasons, so there are definitely people not being seen solely on the basis of money. Moreover, there's an overarching sense of the unfairness of the system (justified or not) on the part of most people I was in touch with, a perception that should at least be addressed openly by the people running these events.
What I'd conclude from all this is that there's definitely a need for a low-cost alternative to the current options, ideally funded by government or non-profit supporters of the arts, to cover the needs of those left out for financial reasons. Whether photographers alone, working in cooperatives or as a non-profit port. review can achieve this is something I'm unsure about. I can only say that general reaction to even the idea of a petition such as I described was lukewarm, at best.