I try to post quickly by building on other people's posts! (Seriously, this has been nagging at me, which combined with its relatively short length, is why it's jumping the queue. Even though it ended up taking longer than I wanted.)
While I was on vacation, John Scalzi posted about science fiction and race [ETA: Wayback version after database crash], saying
My way of dealing with spec fic's racial lopsidedness (on the writing side, at least) is somewhat passive-aggressive: I avoid making any sort of overt racial identifiers at all with my characters unless it's required by the plot, which for my books it generally isn't. . . .
I'm very likely to continue to include non-white characters in my books, because, you know, it's a mostly non-white world. I'm also likely to continue not to overtly note their race unless it makes sense to do so in the plot, because that's the way I feel it should be done. Now, admittedly, this is a chicken-and-egg issue; one of the reasons I can get away with avoiding making race an issue is simply positing the idea that in my universes, race doesn't matter all that much, or at least not for the stories I'm telling in those universes. But then, I don't see that as a bad thing.
I think "passive-aggressive" is the wrong word here. The word I'd use is "ineffective." (Disclaimer: I haven't read Scalzi's books yet, but my understanding of his writing style is such that I don't think reading them would change that opinion.) Since I was away when this discussion started, various people have already pointed out the problem with this approach, in his comments [*] and elsewhere. I'll sum up by quoting Kameron Hurley:
The problem with writing in "race-neutral" (what is that? Gray? Beige?) terms is you get the same problem you run into when you write in gender-neutral terms. As people raised in a racist, sexist, society, we're going to norm a lot of stories, a lot of people, as white males. There are certainly ways you can code this differently, and every reader brings their own unique set of indicators to the reading experience, but I think the vast majority of people are going to sit down and code your world in whitewash unless they get some indication that it's otherwise or they bring something non-majority to the table.
We have a default setting we've been programmed with, and it's the default setting we've been pumped full of since birth . . . .
These are historic holes, ways we view the world, that have been shaped by race and cultural and power and gender. The race and gender and rich land-owning elite in charge . . . determine what we care about and what's important. We can fight against that, and learn more, and question everything, but we have to fight those unexamined truths every goddamn day.
This discussion struck a chord with me because while on vacation, I found myself thinking about the way a specific experience differed from another person's, analyzing all the variables to see if racial prejudice was likely the source of the difference. And it took me literally hours to see a really big variable: the other person is one of the palest people I know.
Let me state this clearly. It's not that I am "colorblind," because I know what colors our skins are. It's that at a very deep subconscious level, I am convinced that I am white. (For those of you new here, I'm not.) That is how strong the cultural default is. The cultural default is white, therefore everyone's white, therefore I must be white too.
I know it sounds ridiculous. It is ridiculous. But it's real.
So, to go back to "ineffective," I mean that in two senses. First, because of cultural defaults, readers are quite likely not to notice that the author has included non-white characters, if the author doesn't do more to specify their race. (Because of mine, for instance, I probably would have passed right by the "clues" (really just one clue, and one not meaningful to many people) Scalzi cited regarding the race of Samuel Young in The Android's Dream, for instance.) Second, to the extent that Scalzi is implying that not overtly noting race in his novels is going to help lead to a less racist society, well, that fails as a consequence as the first problem: if readers don't notice that the characters belong to different races, they aren't going to be impressed that the characters are treated equally. (Compare Rainbows End, which makes a gesture in this direction, even if it does implicitly posit miracles having happened to get there.) As Hurley says, overcoming racist defaults requires actively acknowledging and confronting those defaults.
Which is just another example of what's been said before: completely ignoring race is only positive—or possible—in a non-racist society. Standing alone, then, it cannot be an effective anti-racist strategy.
(For more on this, see the "Color Blindess" and "Writing" sections of 
ibarw's race-related resources post.)
[*] Which, tangentially, is a little refreshing, as it seems like comment sections on writers' blogs are more often knee-jerk defenses of the writer, even when the writer clearly isn't asking for defense. Scalzi actively discourages this, which is one of the things I like about him.
