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I'd also imagine that they have some sort of pressure from yahoo to maintain the strong weighting factor - yahoo is after all a major investor and client of google.
Regarding Looksmart, why do you have to pay to get a listing? Just join Zeal and submit a bunch of pages including your own! And (see other thread), Looksmart links don't seem to count anyway since they disallow all spiders - see their robots.txt file. Zeal links count in accordance with the respective PR of the page from which you are linked so being in Looksmart via the Zeal route does seem to add value.
And philosophically, I agree with all of you that Yahoo, DMOZ, and Looksmart shouldn't be weighted any more than any other place (of course they're not) as the inclusion or exclusion of any page within these index sites confers no greater "seal of approval" than a link from any good site. Many times the links included in these sites are inferior to other sites' links. They are the best overall in a broad array of subjects but in my subject area I know of tons of sites with better links.
To us, at least, a Looksmart link seems to be very valuable in Google, no matter how it actually manifests itself.