I guess the OP would actually want to know why such a functionality is not built-in. At least I'd like to know.

I understand that there is an infinity of ingredients that make up a good search, but surely a trivial implementation would not take too much effort from PG, or at least he could bless an external one and put a form referring to it? A Google ajax search perhaps?

Thanks for the links. Now next time if I need to search HN, I will have to find your comment first (to get links) :) It would be great to have this link on HN homepage. Also, it will help in reducing the duplicate posts. People can do a quick search and check if their topic is already posted by someone else.