Because I'm a fool, I'm going to comment on a gender-relations issue. One would think I would know better by now.
Syp at Biobreak finds an interesting idea from the developers of Prime World:
Prime World has an optional gender bonus: a shield which will automatically deploy if the health of a nearby player of the opposite gender falls below a certain level. This shield is cheap, is in the default talent set for all characters, and is designed to encourage players of opposite genders to fight together. Teams are thus more effective if they are composed of both male and female players. In addition, this bonus helps encourage beginning female players, who feel more helpful when fighting in a mixed group.
All the commenters on the post are pretty appalled at this notion. But is it really that bad of an idea?
Now, maybe the stated rationale for the move--helping beginning female players--is weak. Though maybe it isn't. In the reverse situation, a lot of men would be loath to attempt something that would make them look foolish or incompetent in front of women. Making that situation less likely might indeed make some beginning female gamers more willing to take a chance on a group.
Apart from that, there is a better reason to promote mixed gender groups. One of the greatest strengths and weaknesses of the Internet is that it allows like-minded individuals to find each other and form communities which reinforce each other. A lot of the time this is good. After all, most of us gamers get to participate in a far larger gaming community than we could have in real life.
But sometimes this is bad. There is a portion of the male gaming audience which is very misogynistic. The Internet allows them to find each other, and form all-male sub-communities that reinforce that misogyny, sub-communities which provide validation in the face of wider community disapproval.
A mechanic like the the one above pushes against the formation of deviant sub-communities. Mixed gender groups are mechanically optimal, and thus mixed-gender groups are more likely to form. I think it is harder to retain prejudice against someone when you're playing on the same team as they are. When the rest of your smaller sub-community values them as well.
Basically, if you have a poor opinion of women, and if you never play with women, I would think that you are more likely retain that poor opinion. Playing with good female team-mates forces one to readjust that opinion to match reality.
Another aspect to this situation is that women are often invisible in MMOs. Because the majority of players are men, and a lot of men play female characters, it becomes very easy to assume that every player you meet is male in real life. (What does GIRL stand for? Guy In Real Life.) A lot of women like this invisibility. They don't get hit on, or made uncomfortable, or in any way treated differently.
But there is a price for this invisibility. First, if everyone who meets a good female player assumes she is male, their prejudices can go unchallenged. Additionally, female players seem a lot rarer than they are in reality. If in every random 5-man group, one or two players were identifiably female, a female player would cease to be a novelty, and would be more normal.
Second, by choosing to be invisible, good female players cede defining the image of female players to those who are willing to publicly identify as female in-game. This often means the female players who are willing to trade on their feminity to get material concessions from male players, or to excuse poor play. Those women get to define female gamers, to the detriment of the larger female population.
You see much the same phenomenon with young players. There are a lot of teenage players who are competent, solid players. But they are invisible, and glide by on the default assumption of maturity. You only see the teenagers who are immature and cause drama. Thus all teenagers get tarred by the same brush, and many guilds institute age minimums.
A mechanic like the one proposed by Prime Worlds above might actually have positive effects on the game community as a whole. It nudges or pushes the players towards forming mixed-gender sub-communities as that is optimal mechanically. This makes it harder for misogynistic self-reinforcing sub-communities to form. It pushes women out of a comfortable invisibility, and forces male players to acknowledge them as female and as a significant portion of the community. The community definition of female gamers is more likely to match reality, rather than an unfortunate stereotype.
Between these two aspects, such a gender-based mechanic might actually foster a stronger, better community, despite the initial reaction of many people.