I don't think I would want to go to a "clothing optional" or nude beach. I'd be afraid that I'd be unintentionally staring at people...like "look at her lopsided boobs" or "man, he has a really small..." You get the picture.
I don't necessarily think it's because I would be uncomfortable being... say, topless (I don't think I would feel comfortable going totally nude on a public beach)...but just the ackwardness of staring at people and them staring at you.