My experience with two photography groups - primarily the salon I mentioned above as well as another group that's just starting up - is that photographers who want serious critique will explain upfront what they are asking for from their viewers. So, for example, at the last salon I attended there were a couple people who asked for guidance on portfolio formation, one who wanted to see if his photos were having the intended impact on others, and I asked about paring down a group of photos to a small selection to enter in a competition. If the photographer knows what they're trying to do and explains it, it's much easier for viewers to critique effectively, as they can first discuss the simple question presented before getting into the much more complex why.
In short, for the critique to be useful and to limit the problem of sensitive egos being bruised, the process must be about the photographer's intent as much as the photos themselves. Without that guidance, it's all left to personal tastes, which, as noted elsewhere in this thread, are widely varied but not terribly useful as a means of judgement for the work of others.
