searching isn't like security
Of course google shouldn't open source their 'search algorithm' (this is, PageRank.) The author's arguments that they should are entirely ad hominem and confused, claiming that closing this algorithm reeks of microsoft, and comparing PageRank to system security.
The fact remains that if google open-source's PageRank, spammers will game the algorithm in droves (which they continutally try to do without the source.) Search quality will suffer and the best gamers rise to the top. Consumers lose.
Unlike a security hole in an operating system, which can simply be patched without degrading the system, the only counterattack to PageRank-gaming is to arbitrarily change the algorithm which necessarily weakens search results. This already happens to some extent to due existing gaming without benefit of the source. And not even this would work if the algorithm was open sourced, the spammers would instantly adjust.
A system can be made secure by closing all known holes; a ranking algorithm cannot be rendered ungame-able, by mathematical necessity.
So you don't publish it.