It may not be my place for several reasons to discuss this matter, but I do feel it should be acknowledged. Nerd culture, along with being predominantly male, is overwhelmingly white as well. In fact, nerd culture is strongly associated with whiteness more than it is associated with maleness, as indicated by the song "White 'n' Nerdy" and the commonly phrase "I'm so white" to describe just how nerdy someone is.
Now, I can sort of give anime and Japanese video games a slight pass for having mostly white and Asian characters. There aren't many people of color in Japan, so you can't expect a high level of them in the media. They do exist in anime, of course. There's Anthy from Revolutionary Girl Utena - though I can't shake the fact that she's the most dehumanized character in the entire series, constantly being slapped, literally being treated like a slave and an object, and being extremely passive and allowing herself to be handed from person to person. A better example of women of color in anime is one of the girls in Nana whose name has escaped me since it's been entirely too long since I've watched the anime or read the series and Wikipedia is not helping. I remember her being a much stronger character, but still relatively marginalized. At my panel, a girl mentioned that she understands why there are so few people of color in anime, but she's always thrilled when she comes across them.
The interesting thing when it comes to race and gender in anime is that there are very few protagonists who are women of color. However, in Samurai Champloo one of the male protagonists is dark skinned, and there is of course Afro Samurai, one of the few dubs my anime club agreed to watch due to Samuel L. Jackson's voice acting.
While it's understood why these characters are few and far between, what we need to acknowledge the impact it has on American anime culture. Not only does it perpetuate stereotypes and makes it seem as though anime isn't "for" people of color, it leads to people of color having very few cosplay options if they wish to cosplay within their race - the alternative is to cosplay a white or Asian character, and risk getting some pretty harsh and racist backlash from people at the convention and from commenters on any pictures or videos they appear in. Low representation of a group in any form of media can have a negative impact on that group's psychological well-being and self-esteem, as well as the way they are perceived in the surrounding culture.
What's harder to excuse is the low representation of people of color - as well as Asians - in American comics, video games, webcomics, and science fiction movies, as well as British movies and TV shows commonly associated with nerd culture such as Doctor Who and Harry Potter. These countries have much higher numbers of blacks, Hispanics, and other ethnicities that are barely represented in the media in general. I for one cannot name any black superheros, and while I don't know of every comic ever created, I am fairly familiar with the more mainstream ones. My favorite internet cartoon series, Neurotically Yours, has one black character - a squirrel, naturally, and a very stereotypical black character at that. Not to bash NY too much, I love the series and that flaw isn't really going to change that, but it's a flaw worth pointing out.
I remember watching a friend of mine play a video game with a highly stereotypical black character on it, and when I pointed out the racism he said "nah, he's cool! and it's funny!" Well, easy for white people to find racial stereotypes hilarious, and I'm not saying I don't laugh when black people make fun of white people, but white people are the privileged group, the one in power, so it is different when we laugh at anther race's expense.
Another reason why we see so few people of color participating in nerd culture has to do with the connection between economic status and race. It's not racist to point out the remaining de facto segregation still affecting many African Americans and Hispanics, or the racial gaps in wage, employment, and education. This means that statistically, white people are more likely than black or Hispanic people to be middle and upper class, and that's pretty much the class you need to be in to even partially participate in nerd culture. Being a nerd is expensive! Manga is expensive, anime DVDs are expensive, video games are expensive, going to a convention is really expensive, merchandise is expensive, hell even the cost of comic books can add up. Not to mention, in order to watch anime legally you need to either buy DVDs, get a Netflix account, have cable, or at the very least have an internet connection that supports streaming (it's really frustrating to watch anything on a slow connection) - all of which cost money, though these things are usually taken for granted by most people in my anime club. Schools that have anime clubs are typically the wealthy schools mostly attended by white kids, whereas inner city schools that are predominantly attended by African American and Hispanic kids hardly have the money for after school clubs at all. Get anime from the library? Yeah, a good library in a middle class community perhaps. People in low income communities simply do not have the same access to nerd culture as people in more affluent neighborhoods. Unfortunately, the costs associated with being a nerd can skew the racial makeup of the subculture.
There are multiple systems of privilege that exist in nerd culture as well as American society as a whole. The main difference is that nerd culture prides itself on being so egalitarian and so "past" discrimination that they feel it's okay to engage in "ironic" sexism and racism, and they don't ever feel the need to examine their privileges even for a second, because they're "above" needing to do so. Any hint that this isn't true, that nerds are just as susceptible to discrimination is dismissed at best and met with anger and extreme defensiveness at worst. This, and the fact that I'm becoming increasingly involved with the subculture, is why I am now choosing to focus on the systems of privilege, especially gender dynamics, within it.