In addition to hkabla's answer, I'd like to point out that Google wasn't very happy with the thought that its name will become a regular verb that stands for any use in a search engine (for example: "I googled her at Yahoo!."), since it will mean that the strength of the Google brand will weaken, as it becomes a generic term. I think that if Yedda will become over the years as powerful tool as google is, then it too won't be happy with the idea of becoming a generic term.