I've always kept Ketchup in the fridge, but a breakdown on the hot sauce thing from my perspective: It's not bad or anything, just weird. Growing up I've been to a variety of houses where people had hot sauce. The whities always had some crap like Tobasco (for "kick", not flavor..which is a double failure there) in the pantry, black friends usually had a variety of brands that I don't remember (in the pantry, again), and Asian friends always had Sriracha on their dinner table. I've always thought the Asian friends had the right idea. Hot sauce is more like salt or better where you adjust to taste for a variety of meals at the table. Ketchup if fine in the fridge because you know that the amount you put on or on the side of what you eat is enough, but sometimes the taste for hot sauce changes, like with salt or pepper. Keeping it in the fridge just seems weird because you don't need to.
I also don't mind if the ketchup is cold. I like that contrast in temperature. It's why I like putting a tomatoes/lettuce on a hamburger or taco.
