If anything, that sounds like a solid argument to decentralize it. I don't want China's government, white supremacists, churches, soccer moms, Jihadis or grievance-of-the-month activists controlling how information is indexed; I would rather use multiple indexes that balance out controlling interests and biases.
Unfortunately if it's decentralized, then it becomes controlled by spamlords, SEO artists, advertisers, and anyone else who stands to gain from manipulating the index to their advantage. At least if it's centralized, the fights are out in the open and have a chance of converging on something reasonable (like e.g. wikipedia).
