>The basic principle of decentralised search is an individual only needs a tiny fraction of all knowledge available, That may be a reasonable assumption but it

>The basic principle of decentralised search is an individual only needs a tiny fraction of all knowledge available, That may be a reasonable assumption but it omits a major tradeoff: some types of "knowledge" require the search engine to "see" the entire index and synthesizing such knowledge cannot be delegated to decentralized nodes. To reduce the search engine tradeoff to a simple math analogy: You can "decentralize" the calculation of a SUM to individual nodes. However, you can't decentralize the calculation of an AVERAGE. Divide-and-conquer strategy of calculating an average will give the wrong result.[1] Some searches are like "SUMS", and some are like "AVERAGES". If a search is pure text retrieval without regards to relative weighting or ranking, decentralized nodes with each holding partial segment of the index will work. (E.g. you want to retrieve a chili recipe so your search query hits the decentralized node that has recipes starting with "C" or whatever hash algorithm.) That's a "SUM" type of problem. However, if you want to find the top 10 ranked recipes by links, the decentralized nodes can't answer that. That's a "calculate the AVERAGE" type of problem. Also, determining which webpages in the index are "fake news" or SEO "link farms" and other "bad actors" is also an "AVERAGE" type of problem. The machine learning algorithms need to see the whole index (or pedantically, a very large portion of it) to "learn" what "fake news" looks like. Google's ability to comb their entire index in a centralized place lets them discover new insights to evolve the Pagerank algorithm from Panda->Penguin->Hummingbird->etc.[2] Yes, you gain more privacy with decentralized or p2p search, but you also lose the ability to search on certain types of queries. [1] https://math.stackexchange.com/questions/115091/is-the-average-of-the-averages-equal-to-the-average-of-all-the-numbers-originall https://math.stackexchange.com/questions/115091/is-the-avera... [2] https://conversion-hub.com/wp-content/uploads/2016/08/Comparison.bmp https://conversion-hub.com/wp-content/uploads/2016/08/Compar...