After sharpening just about anything, I'll often cut a tomato just to make sure it's up to snuff!
Plus, on the road or at work, I'll use my E.D.C. folder (usu. BM 940 or Kershaw Shallot) for food prep (tomatoes, apples, salami and cheese, fruit for mixed drinks, etc.) If I last cut something sticky, I'll wash it first - but usually just a quick wipedown.
If I was afraid to use it for food, it wouldn't do me much good to carry everyday.
I always wash it after sharpening/honing, after food prep, after cutting tape/adhesive/messy stuff, and every few days just in case - so it isn't usually very dirty.
I've only used it in a restaurant once - my daughter had a particularly tough hot dog, and they did not provide a knife. I felt a little self conscious, so put it away quickly after wiping it down.