It's fairly obvious that on a man, a veined and muscled body is a symbol of strength and, let's face it, virility. Is it just a coincidence that Justin's arm is right in front of his crotch, acting as a stand-in for his penis?
Meanwhile, Madonna's veins are seen as some kind of flaw; people instantly think of her age, of aging, of wrinkles and old ladies. Women are supposed to be soft, not strong, and young, not old. Which is bullshit. Of course.
As one commenter noted on yesterday's Madonna post:
Good heavens, I love her veins! You get veins like that from being active or working hard - those are not easy to come by! It's a shame that we worship the muscle but look down on the vessels necessary to nourish and restore that muscle.
I'd have been shocked if they had left her veins and upper arm definition intact, to be honest. I love to look at strong bodies and lift heavy weights, but the backlash against arm muscle definition in women is rabid.
An interesting, sad, backwards truth: Women in this society are pressured to be thin, but when you look like you've worked hard for your muscles — Madonna is a yoga, Pilates and dance enthusiast, after all — it's considered grotesque and in need of smoothing for a fashion ad campaign.
Men, on the other hand, can look as strong as they want to.