Well not on real leeches, those wonderful little yummy bugs. :) But the leeches we are talking about are those evil search engines, specifically the ones that charge you for those rankings. Pretty much everyone has heard about Jakob Nielsen's recent article he named Search Engines as Leeches on the Web. In response to that, Danny Sullivan (our industry leader) started a Search Engine Watch forum thread he named Search Engine Leeches, Dependency & Losing Perspective. The thread has some really excellent responses.
Danny seems to clarify that Jakob Nielsen's article is mostly referring to the PPC side of things. And he explains that most Webmasters should not solely depend on only search engine traffic for their Web properties (the dependency part). Let me pull out some of the excellent comments in that thread.
projectphp: "One thing though: shouldn't the SEM community be proud that people have overblown how important it is?" So true!
massa: "Maybe I missed the "big picture" with his post but I didn't get that his point was to not want, wish for or work for search engine traffic. I thought his point was that the underlying motivation of search engines is changing from wanting to be a library of sites to send people to, to becoming a destination site which would in essence make them not the sender of traffic as much as the stealer of customers."
cre8pc: "Why the push to be liberated from seach engines and turn to other forms of marketing, from a usabilty guru? Well, of course. Duh. Marketing was never just about rank or PPI."
Oh, ThreadWatch reports that Brett Tabke Challenges Jakob Nielsen to Block the Bots but if this is not about organic results then the challenge is not relevant. But the challenge is exciting based on his rankings for this little keyword phrase.
Forum discussion at Search Engine Watch Forums.