Vitiligo is pretty common, with 1% of the population having some vitiligo. Given that I am white, it's not much of a problem for me, but I do have quite a few patches on my body from it: jaw, neck, stomach, arm, groin area, knee, fingertips. Only really noticeable to others when I am tanned and of course I need to protect that skin more from the sun. The strangest thing is that the hair which grows on those patches is stark white.
Anyway yeah, very common. No problem for white people really, but if you naturally had dark skin, guess it could feel uncomfortable. Chances are a few people posting here have it and just don't realise.