I wore a white belt today. Matched my white/brown shoes, the bit of white in my sweater (and polo shirt beneath), and my hat. Got it two days ago. It's an IZOD reversible, but since the edges are white I doubt I'll use the black side (plus I have a black belt already).
felt weird posing and had to resist the urge to stick out my belly (for some reason that felt natural when trying to stand on a step stool in my daughter's bathroom [hence the pink] and take a waist-high picture with the iPhone...???).

BTW, rolling your sweater up makes you look really really cool. Try it sometime.
Anyway, belt wasn't really visible, but I still don't have a problem with white belts. I don't think people with large midsections should wear it, but they also shouldn't wear white pants with a black belt either - contrast draws eyes, and if it's something you'd prefer to "hide" a bit don't use contrast.
Warning: Spoiler! (Click to show)
P.S. tucked it a bit so nobody would get jealous. 