They're not for everyone but they sure are tasty! This is part of the Chinese influence in this country. I'm told by one of the Filipino midwives that it is made by boiling the eggs then burying them underground for several months in mud! That is what causes them to turn black!
Here is Jordan, one of my classmates, tasting a century egg for the first time! She thought it would be bad... but they taste like regular boiled eggs but the texture is a bit different! :- )