LOL Recently I started to believe that restaurants deserves our feedback... I wouldn't make them remake the food (hell no, I'm worried that they'll spit in my food too), but I'll tell them what's wrong with it at the end if it was really bad..
Last time I went to a very very posh restaurant where food there was meant to be AMAZING.. but there was this one dish that was so salty that i could only have 1/3 of it... It's a degustation menu so they can see that you haven't finished your food... so I had to tell them that I found the dish rather salty... and I think Kev was really embarrassed that I said something about it LOL