I came here to see if anyone would express my (probably unpopular) opinion that mayonnaise is disgusting. I see that that has not yet happened.
I was surprised to see that in places like Netherlands and Belgium, where french fries are a popular snack, that people take the option of eating them with mayonnaise.
It's a matter of habit, I guess. When I told a Dutch friend that I couldn't imagine eating french fries with mayo, he told me, "I can't imagine eating them with ketchup."
In several restaurants during my travels in Africa, I would order a salad. All the ingredients were listed, so that was fine. Then, when the salad arrived, I saw that it had a huge glop of mayo on top of it, even though it was never listed as an ingredient. I eventually learned that I had to tell the server, when I ordered my salad, that I did not want mayonnaise on top of it.