> I wondered why patents are no concern for a competitor of Google (they have various broad and trivial patents on using historical data, user feedback, moderation for better search results).

How exactly are server-side patents enforced? When the hardware on which the infringement is occurring isn't exposed to the public, how can anyone verify its presence? I know that for some (many?) of Google's search patents, there might be an indication on the client side if infringement were occurring, but I imagine that there are also many patents for which this isn't the case.