Interesting because it does make it harder for a curious straight friend to find out that you're gay, but it's still not impossible. If you're that concerned about it, I don't think OKCupid is really the route to go.
If you're not so concerned about it but would rather not be out to the world, this could be a good means for that.
If you're not so concerned about it but would rather not be out to the world, this could be a good means for that.