In England we have something called "Marmite", in Australia I believe the same product is called "Vegemite". It's basically yeast extract which is a by-product of beer brewing. You spread it on toast and eat it, very much like jam... but the taste is NOTHING like jam. It's an incredibly thick, strong, salty, pungent taste and, much like natto, people love it or hate it! So much so that the advertisers actually made this their slogan!!
I think most cultures have one of these staple "love or hate" foods. The Chinese have something called chou doufu (fermented tofu) which apparently stinks to high heaven, but is incredibly popular.
Personally, I don't do natto, Marmite, Vegemite or chou doufu. "Uni" (sea urcheon) and "shirako" (fish ovaries) are also out! I'll try anything once, but with somethings... once is more than enough.
After all, I've only just got used to eating chicken cartilage!!