I've been browsing through some of the sex topic images on Wiki to decided whether I think drawings would be better than photographs. I'm leaning towards photographs (well done ones, not phone cam cock-shots).
This possibly swung the balance for me:
That is, apparently, a depiction of male masturbation.
Would users, of whatever age, be better off seeing that, a professionally-photographed image, or nothing?
Also, to be frank, do we really want the younger generation to experience their first images of sex through (what is undeniably) porn via DVDs and hardcore sites? At least the phallic shots on Wikipedia aren't large, by any stretch of the imagination, so there will be no insecurity issues - compared to if a 12-year-old saw John Holmes's dong.