(Blog Azeroth has weekly shared topics. I generally don't participate but this one interested me. You can find other posts here.)
If you look at recruitment posts often enough it is not uncommon to come across a post that says something to the affect of "No Women" or "18+ Only." Some people look at these type of rules with disdain, because they show prejudice. However, when I was looking for a new guild nine months ago, I loved them. They gave me great insight into the competence of the guild leadership, and told me I probably wanted to avoid the guild.
Now this is not, going to be a long post about how these policies are Sexist or Ageist. They are, but like it or not there is some practical reasoning behind the rules. Kids to tend to be more immature then adults. That doesn't mean that kids can't be mature or that adults can't be immature, but in general I think its true.
From a sex perspective, I do think the presence of women in guild opens the doors additional risks that would be less common in an all male guild. For one, some men insist on acting like idiots around women. It's not the woman's fault but something that has to be dealt with. Second, It seems to me like women are more likely to have an RL relationship with a guild member. Which can lead to uncomfortable situations like this one found on WoW.com. Worse still, I've seen situations where real life Husband/Wife drama spills over into the guild.
Like it or not, these are real issues that have to be dealt with by guild leadership. However, instituting a straight ban on women or kids is just lazy way to deal with the issue. What it said to me as an applicant is that when a problem presents itself to the guild, the leadership took the easy way out. They would rather cover up the problem then fix it, and why would I want to be a part of a guild like that?
A good guild leader would deal with the issue/person instead of making a preemptive ban. If a male member is acting like an idiot, deal with him and not the girl even if he is the main tank. If the female player isn't good enough for your content, then be honest and work with her. If it blows up, at least you tried. Plus I have to believe that there are ways to identify problem players from the application process. So, when I see a ban on a recruitment post I know the guild has management issues and would probably end up disappointed if I joined the guild.
On side note, a vast majority of the women I've played with have been great. I think they are the norm rather than the exception. By the same token it was months before I learned that a member of my guild is still in high school. He is great to play with and I would have believed him if he had told me he was 30 years old. The guild that uses bans would be missing out on great players, and are diminished because of it.
Edit: People seem to be not reading my post or missunderstanding it in mass. I want to make a couple of things clear. While I think the presense of women in raiding guilds can potential bring addtional issues to the surface, I in no way think those women are the cause of those issues or at least in a higher degree then the men. I have played with just as many if not more whiny, loot whoring, men as women. I in no way advocate a preemptive ban. In my opinion, guilds that do have leadership issues, because they deal with the stereotype instead of the problem.