As for keeping volunteers equal to avoid the problem, that need not mean keeping everyone identical. Leadership roles can rotate, with finite term limits. That way every leader today knows they will be the underling tomorrow. (This also keeps everyone interested and motivated as nobody is every stuck on one task/job).
But is that inherently a bad thing? The way you state it, I'm getting that you're implying that it's bad 100% of the time. If you're looking at it in terms of black and white, I guess just hearing "rules can be bent" is bad, but I don't think it's that simple.
I think there are times where the rules can be bent which creates an outcome that is beneficial to all. Times where the rules don't account for certain variables/situations and those incidents need to be handled differently (or with care). I think it's a complex problem and it may need a complex solution.
The best, and I mean absolute best volunteer teams I've been a part of have always had a leader at the top with absolute authority. However, he or she never abused their power, and rarely flexed their absolute authority, preferring to take up the mantle of "benevolent dictator". In those cases, some amazing things happened. We got our work done ahead of time, group moral was sky-high, and the projects were a massive success. Things "just worked".
http://meatballwiki.org/wiki/VestedContributor
VestedContributors think the rules can be bent for them because they've been around so long and done so much good work.